If stimulating yourself is the only way you know how to, then I'd tell him that. Maybe the first time having sex, I wouldn't fake it, but I'd just act content with only him finishing. Once you get more regular, I'm sure the conversation can't be avoided. Then, once you get more comfortable, yoou can try to relax and see if he can do it to you. But, the man shouldn't get mad because you like what you like. Isn't the reason for sex to feel good?