Op, there's nothing wrong with your boyfriend! Don't mind all these hypocrites talking trash here about rituals. Your guy just adores you and find rimming as a way of expressing how much he desires you.

Like someone said up there, you must be neat and perfect enough for him to crave you to the point of licking your butt. I've been there and done it. There are some caliber of girls you'll be with and you'll feel like eating up everything from them. Rimming is even small, I've begged a cute girl to pee into my mouth before.

It's a way of expressing how deeply you desire your woman.