Sexually Frustrated

Today has just been a stressful/aggravating day! My boyfriend and I haven't had sex in 5 days, (that's a long time for us), and in my mind I was thinking all day, "I need to have sex and release this stress." Well night time rolls around we get down to buisness, and I can't cum. I go from really turned on to off in a second I don't know what happened, but automatically things dry up and we have to end quickly. After sex I just start crying because I'm so mad that I didn't orgasm and all this stress from the day is pinned up inside me.... does anyone else get inside their own head where you can't even relax and enjoy sex?