Masturbation

So I’ve been dating this guy for almost two months (we’ve known each other for a while and are very close) and are getting pretty sexual. But the problem is is that I can only cum when I’m on my stomach and rubbing against something— or at least I’ve never been able to any other way— and he always feels really bad for not being able to make me cum. He also has giant hands so fingering me feels a lot different then when I do it myself and it hurts too much. Anyway. Any tips I should tell him to do?

P.s. I’m 15