sensational numbness

I have never thought about nor wanted sex. I have never really ever been "turned on", according to my friends descriptions of it, nor have I really felt true compleat physical attraction, again on the basses of what my friends have told me. I did consent to sexual intercourse with my partner last week though. My issue, however, is I felt nothing at all. I mean at first, there was a brief moment of pain, but that quickly subsided into nothing. I wish only to know if there is a reason for my lack of response or felling. This is not the first time that I have not reacted or felt anything, but this is the most extream. I love him so much. So I do not think it's a mental block. Any ideas?