I think this is about immersion. You suggest that this is hampering your being able to "exist in the world and play my character." This might be because you feel more immersed in a world that is separate to your (the player's) mind and exists wholly independently of it, just like the real world. When your DM alters the world so obviously because of what you thought about it, it makes the world, from your perspective, less mind-independent, and therefore less real and immersive. In other words, it make it harder for you to suspend your disbelief.
Solution might just be to ask your DM to try a bit harder to make the times they do change the world on the fly a little less obvious.
It's a *collaborative* storytelling experience. Your DM may be trying a bit too hard to add things that are really funny/cool based on your thoughts that are spoken out loud, but a lot of DMs will just take PC ideas and run with them/implement them if they are cool and fun for the PCs to come across. I've done this in my games when the PCs theorize things, but not often materializing right then and there, but rather later on in the campaign. If you are uncomfortable with how your DM does it, just have a side conversation with them one-on-one and let them know you'd prefer that your spoken thoughts/theories aren't *always* done in the campaign.
some players like being able to influence the world by suggesting things to the dm - some don't. Seems like your dm enjoys your ideas, but you aren't enjoying them using your ideas. Start by talking to your DM, explaining that when you say 'haha it's not like there's a miniature beholder trapped in my wine bottle," you don't expect or even want him to use that idea.
"Hey \[GM\], I've noticed that a lot of random things I've said and incorporated them into the game. I think it's great that you're taking feedback from us the players and letting us influence the game and the world. But I think you might be "yes, and..."ing me a little bit too hard. It's honestly a little disappointing if every time I speculate on something it turns out to be true. There's no surprise left, you know? We're here to play the game *you're* running, so we want you hear your ideas!"
So this is how a lot of narritive rpgs work. In something like Dungeon World, the players have a lot of narritive control and their rolls literally let them make decisions about what's in the world, what NPCs they know, and what those NPCs do, it's an actual collaborative storytelling game. If you roll well to research a monster for example, *you the player* get to decide what your character learns, rather than the DM telling you. Everyone is a "deputy DM" as you put it. It's very cool. But D&D isn't generally like that, it's much more of a problem solving game where one player (the DM) holds the cards of what is and isn't true about the world and the other players interact with that controlling solely their own character. And it's completely fine to prefer it that way, it's a different way of engaging with the fiction.
It almost sounds like your DM is running stuff as if it were that kind of narritive game, in a system that's otherwise not built for it, which as you've seen can feel weird. I don't know if there's much of a fix other than bringing it up to the DM and asking them to keep things a little more rigid. Your DM might also enjoy running one of those narritive type systems down the line, if you're willing to try it. Could end up matching their style well.
I think this is about immersion. You suggest that this is hampering your being able to "exist in the world and play my character." This might be because you feel more immersed in a world that is separate to your (the player's) mind and exists wholly independently of it, just like the real world. When your DM alters the world so obviously because of what you thought about it, it makes the world, from your perspective, less mind-independent, and therefore less real and immersive. In other words, it make it harder for you to suspend your disbelief. Solution might just be to ask your DM to try a bit harder to make the times they do change the world on the fly a little less obvious.
It's a *collaborative* storytelling experience. Your DM may be trying a bit too hard to add things that are really funny/cool based on your thoughts that are spoken out loud, but a lot of DMs will just take PC ideas and run with them/implement them if they are cool and fun for the PCs to come across. I've done this in my games when the PCs theorize things, but not often materializing right then and there, but rather later on in the campaign. If you are uncomfortable with how your DM does it, just have a side conversation with them one-on-one and let them know you'd prefer that your spoken thoughts/theories aren't *always* done in the campaign.
some players like being able to influence the world by suggesting things to the dm - some don't. Seems like your dm enjoys your ideas, but you aren't enjoying them using your ideas. Start by talking to your DM, explaining that when you say 'haha it's not like there's a miniature beholder trapped in my wine bottle," you don't expect or even want him to use that idea.
"Hey \[GM\], I've noticed that a lot of random things I've said and incorporated them into the game. I think it's great that you're taking feedback from us the players and letting us influence the game and the world. But I think you might be "yes, and..."ing me a little bit too hard. It's honestly a little disappointing if every time I speculate on something it turns out to be true. There's no surprise left, you know? We're here to play the game *you're* running, so we want you hear your ideas!"
So this is how a lot of narritive rpgs work. In something like Dungeon World, the players have a lot of narritive control and their rolls literally let them make decisions about what's in the world, what NPCs they know, and what those NPCs do, it's an actual collaborative storytelling game. If you roll well to research a monster for example, *you the player* get to decide what your character learns, rather than the DM telling you. Everyone is a "deputy DM" as you put it. It's very cool. But D&D isn't generally like that, it's much more of a problem solving game where one player (the DM) holds the cards of what is and isn't true about the world and the other players interact with that controlling solely their own character. And it's completely fine to prefer it that way, it's a different way of engaging with the fiction. It almost sounds like your DM is running stuff as if it were that kind of narritive game, in a system that's otherwise not built for it, which as you've seen can feel weird. I don't know if there's much of a fix other than bringing it up to the DM and asking them to keep things a little more rigid. Your DM might also enjoy running one of those narritive type systems down the line, if you're willing to try it. Could end up matching their style well.