bottom tips?

hey guys, since I have no gay friends to talk about this, maybe you can help me. I'm really skinny, and it kind of lows my self esteem which generates some insecurities about my body, especially my butt. so how do you exercise your booty? mine has no shine and I just want to feel good when I'm with someone but for that I first need to feel good with myself. also, how do you get prepared for sex? what do you do to feel relaxed about the anal pain/hygiene? I always feel like something could happen and it would be so embarrassing :/