I once told my boyfriend I was into animals. He then kissed me, held my hips and claimed me. Yeah I love my dog.
Lol, sorry for my joke, now on a serious note
This is quite a dangerous step, nobody knows you and your boyfriend better than you do, therefore nobody here can give you answer that would be reasonable and would satisfy you. I would probably go for a series of hints, make some allusions every now and then, maybe in jokingly tone, look for what his reaction is like, if he is disgusted, or smiling, or wondering, whatever, that can give a lot. Take your time, maybe at some point he starts making hints/suggestions himself, then it's quite easy.
Whatever you do tho, be careful, and don't mention it explicitly unless you are really sure. Not only that it can end up with a breakup of otherwise perfect relationship, but it can lead to slandering and some other problems in your life.
Maybe ten girls will tell you that it went fine. That's not guaranting it will be the same for you, don't lose your guard.