Hi,
You need to have an honest discussion about this kind of sex. He is the only one who can tell you if he tried it with a man. I could tell that you don't feel comfortable about anal sex. He should not force you to do it. You both have to agree on how to please each other sexually.
Straight men also do anal sex, it does not mean to say he has done it with a man.
He should respect your wishes, if you don't like it , then he should not insist. If he loves you enough, he will understand you and probably wait until you are ready for anal sex.
Take care.