Unable to orgasm

Alright, I used to orgasm everytime my bf went down on me. But lately I just can't. Not by penetration, clitoral stimulation, nothing. My bf got so frustrated over it the other night he ended up yelling and we got in a fight over this. What's wrong with me? Could it be stress? Should I go to a Dr or a sex therapist. After last night I'm scared to have sex again because I don't want to upset my bf. I don't want to fake it either, cause that would probably make it worse.

It's not that I don't enjoy sex, I love it. I love feeling intimate with my man, bit his mind is so focused on the climax. I don't really care of I do or don't cum most of the time, I just like the enjoyment of sex.

Help, advice, comfort, anything!!!