I can't get off..

Okay so this might sound strange or weird, but I cannot seem to get off whenever my boyfriend goes down on me. I have gotten so close and I can never fully get off. The poor guy will be down there for ever trying his best. When I masturbate , with my bullet , I have absolutely no problems. He keeps telling me that I need to communicate but I'm still sorta shy when it comes to telling him what feels good and what I like. Please help. We both feel awful because he can't get it right.