boyfriend can't come from head... help !!

I'm in a relationship with the most amazing boy I've ever met. We've been together just over a year and even though I want to have sex with him I'm just not ready yet.. With ex boyfriends head has always been a strong point for me lol but with my current BF he just struggles to orgasm from it. I've made him come twice from head but every other time he has to finish himself off. the two times he did come he was either standing up or sitting upright.. Recently we have been doing it with him laying down in bed, do you think the position could be the cause ??? Any tips to make it better for him ladies??