My boyfriend is younger than me. He claims he is a "big fan of butt sex", and he loves oral. But I'm just concerned because people have been telling me he might be on the DL, Bi, or gay. He only wants to penetrate me in the butt not the other way around. I was trying to test my theory so I put my finger on the top of his butt hole and he freaked out.Should I be worried that he would be willing to receive oral and give anal to another man?

How old are both of you?

When someone says that their partner is younger than they are, I like to make certain of the ages involved before giving advice.

I'm 20 he is 18 going to be 19 in April

No it does not mean he is gay or bi, if he was gay or bi he would want a man there to be having sex with. He merely likes sex that way, if you don't, tell him and don't do it, if you want it other ways, you take turns doing it differently if that is OK with you. Many couples like it any and every way and change off all the time. Others only do it one way in one position and that is it.
You and he need to sit down ( not in the bed) and talk about it, what you like and want, and what he likes and want, and work out a plan that will work for both of you

I think you should ask him. What you will probably find out is that he likes the sensations of the tighter passage. It is probably closer to what he is used to with his hand during masturbation. There may also be a part of his mind that is thinking about pregnancy or rather preventing it. He may have a 'butt' fetish and likes their look, feel, etc. much like someone with a leather fetish likes leather. Only he can tell you.

If you prefer vaginal intercourse, tell him. Talk with him. It's your body and you can tell him no if it bothers you. If he doesn't respect your needs then is the one you want to be with?

You have to decide what your into.. he was upfront and honest it sounds like. By saying he's a fan of butt sex. Now you be open and honest as well. Most men like anal. I don't think being gay or.Straight has anything to do with it. If you don't like it though, you shouldn't do it. Js;)

They are both feel different... likely as was mentioned his fear of making you pregnant plays a factor... personally I like both, but if you carefully word it... and present it the right way to him... I'm certain if he's any sort of man he'll swing it more towards 50/50 just to please you. And you both get it the way you like it best plenty of the time. And its good to switch things up from time to time to keep it fresh and not become repititious.

Its got nothing to do with bi or gay tendencies at all.