My boyfriend is forcing me to have sex. But im not ready for it so im refusing. Does it affect his health if he control his sperms?

NO. There is no negative effects on his health. If you are not ready for sex, then continue to refuse. If he continues to pressure you, then he is not interested in a relationship, just sex and he can handle that on his own. A true boyfriend is not going to pressure you to do things that you do not want to do.
NO. He has ways... Do not let anyone force you to do something you feel strongly about not doing. I commend you for that.
Myth. Some guys will tell you anything to get sex.They may even believe it because their friends told them. He will not loose his ability to have kids, nor have his testis explode. Sex should always be a shared experience.Never given or taken. He needs to respect your wishes or hit the road.