Is it wrong that i don't trust him because of this TINY thing that happened?

[i love you more]

Okay, well I'm close friends with this guy, and we are probably going to end up dating. When we first started talking a few months ago, I had posted this picture of myself on twitter. There was a tiny bit of cleavage that he pointed out, and I told him that I had cropped out more cleavage from the original picture. He jokingly asked to see the first picture afew times, and i said no and he gave up. A few weeks later, i made a Facebook status about how annoying it is when girls get a new boyfriend every day, and I told him that this girl who had commented on it was the one i had made the status about. He said if i didn't send the original picture, he would tell her i said that, and he was being totally serious, so i had to send it to him.
Now were closer and all, but every time i'm about to tell him a secret or something, that comes to mind, and i can't bring myself to tell him.