Boyfriend never made me cum.

I have been with my boyfriend for almost 3 years and he has never made me cum. We have been having sex for around 1-2 years. It's not as bad as it sounds, we are such an open couple and he knows very well what I like because I tell him and we try loads of different things but it still doesn't work. Can someone please help, maybe we don't have sex for long enough but usually we go for about 10-30 mins???