There's no such thing as penis growth exercises. That is a myth; it doesn't actually work. If your boyfriend is truly 9.5 inches that's rather large, especially for a thirteen-yaer-old, but it doesn't necessarily mean there is a health problem. It's possible there is one, but he may just be really well endowed.

I would also suggest starting some sort of birth control if you are interested in having sex. It;s very important to do your best to prevent pregnancy. If you're worried about his size I would suggest talking to him about going slowly and using lube. Remember, it's all about your comfort, and he doesn't have to be all the way inside of you for sex to feel good for both of you. I also want to remind you that you should't have sex unless YOU want to. If you feel ready that's fine, but don't let him pressure you into sexual activities you don't want to participate in. IF he's not respecting your boundaries that's a sign of an unhealthy relationship and you need to talk to him.