>>29260413>What does it feel like to have a guy's shaft go up in you?Depends on how experienced you are. If you've never had anything up your butt before, the old joke that it feels like "pooping in reverse" isn't that far off the mark.
But once your brain gets over that initial association and you get used to the feeling, it just becomes it's own thing. Anal/prostate pleasure is very different than penile stimulation. The feeling is more intense, but also more spread out, and emanates from your gut instead of being laser-focused on your dick. In some ways, it can feel like you're scratching a deep itch you didn't even know you had.
>Do you actually feel a different between protection or raw?For the bottom? No, not really. There's a slight difference in texture and friction, but if it's enough to notice that probably means you're not using enough lube.
>What's it feel like when he busts up in there?Despite what porn would have you believe, you can't actually feel the cum deep inside you. Not unless he's cumming so shallowly (or so voluminously) that it immediately spurts out of you. If he's the sort of top who keeps thrusting through his orgasm, you'll feel his friction change as his cum adds lubrication, and you might feel his cock swelling and twitching inside you, but you won't feel the cum itself until it leaks out.
>How much of it is psychological?Depends on the guy. IMO a good 90% of the pleasure of getting fucked is purely psychological. I'm not the biggest bottom though, and don't enjoy it enough for e.g. finger or dildo play. Some guys get absolutely addicted to the physical sensation though... deriving pleasure from your butt is kind of a skill you can build over time.