Well I don't know for sure how it feels, as I've never had a guy inside of me. lol
But hey, Imay not have first hand experience, but I can still tell you what my girlfriend says about it, and what a couple of my ExGFs said about it. Simply put. They usually can't feel it while it's happening. If I came a lot they might say they could feel that after the sex. Like it's just a lot wetter or something similar. Heck there are guys who fake an orgasm by just making retarded faces and grunting out the words "I-I-I'm coming..." I don't think you're likely to be missing a whole lot by not doing it.
Still if this is what you want, you can always just do it if you feel the birth control is enough. Heck me and my girlfriend still haven't slipped any past that guard. So if you want to bring it up with your boyfriend I see no reason you can't take the direct approach. Like for example just telling him that this is something you've been thinking or fantasizing about, and you've been curious about it. Then talk about it a bit. Ask him his thoughts on it, and see if he's responsive. If so, then just request that he does it next time. Maybe even exclaim the words "Stay inside" when he's about to blow his load.
Really there isn't a wrong way to handle this. If you've been dating him for a few years, I imagine talking about this with him is something you'd be more suited for than any of us. You'd probably know more about what he wouldn't respond to, so just rule those out, and go with the best option you can think of. Or just go with my idea. Whatever.
Anyway good luck with this. I hope it works out for you.