Guys, & Gals, if he swears about it being true, and then swears it was a lie!?

Okay, here it is....if the guy you've been seeing for a while tells u he had an intimate encounter with a female that I knew at a strip club, and b4 u blow up, u ask him to swear that it happened, and he then swears that it did, but suddenly after I started to break, he says, no no no, I swear I was just kidding! What would u all believe? Again, he swore it happened, but when I started to break down, he swore again, it was a JOKE! Which would u beleive? Also, while he was telling me abut it being true, when I began to ask, "are u serious", he was very nervous, and could not sit still, he grabbed me saying, WHAT, do u know something bad about her that I don't know! Ok, feedback time, and please, honest replies please!!!!