I'm not sure what to do

This is just my oppinion and everyone feels different about this but I've never ever suck 🍆and never interested in doing something lik that.My bf is asking for me to do it for him but I honestly think it's disgusting and he's saying that if I don't do it eventually then basically we can't be together.I mean I'm trying to consider it but honestly I don't think its right for him to call me selfish when I've treated him way better than anyone he's been with.