Is it normal not to enjoy sex at all?

I have been having sex since I was 14 and barely ever get off. Oral, fingering, intercourse does nothing for me. I feel like it's a job and that it's not worth it. The only way I can have an orgasm is to use a really strong vibration. This really puts strain on my relationship with my boyfriend and father of my children. Is this normal and what is you advice?