Ok my problem:
I have been dating my BF for 14 months and our sex life has been great. In the beginning of the relationship (like in the first month before we became serious) he cheated on me once, the same night he called and apologized, I met the girl, he told her in front of me that he made a mistake he wanted to be with me he was sorry but that he would never see or talk to her again (he had met her one night and same night he slept with her).
We worked on our relationship, worked it out and got serious. He takes me everywhere with him we are together non-stop except while he's at work and he calls me either on my cell or at home on all 3 breaks plus sometimes in between when he can sneak in a call without his boss seeing him.

Basically everything has been good until last night...
we were being "intimate" and usually I'm a fairly "dry" girl no matter what we do, oral or whatever I'm usually "dry" well for some reason after giving him "oral" I was obviously ready and excited and when we started to have s*x he pulled out and asked me who I had been with earlier! I was shocked because I have NEVER cheated on him! NEVER! I thought he was implying I had an odor or something and I was like

but he said that I had "juices" down there that weren't usually there! He said they were "milky" like a guy's. They couldn't have been his because I had showered and all (obviously) since the last time we were together which was the previous night. He knows I've never been like that "wet" before so he is thinking someone else left something in there but I don't know why I was so wet or rather that is normal or not, also I don't know how to convince him I didn't cheat! I swear I didn't if I would have I would have clearly confessed I'm woman enough to stand up and accept responsibility for my actions but since being with him I've never cheated!
Anyway I'm seeking advice on how to convince him and show him I didn't cheat on him. Is there anyway I can go about doing this?
And has any other woman ever had this problem about normally being "dry" then all of a sudden one day you are overly "wet" then dry again the next day or could there be something wrong with me?