You tell him exactly that. You got it from a cheating boyfriend. I have delt with this situation with another friend of mine. Her boyfriend had it. Had not had an outbreak but still Gave it to her. He didn't know that by not having an outbreak you could still pass it on. Well she started having problems about a year after they were going out. Both went to the Dr. THe Dr asked her who she had been with, which made her mad cause she hadn't been with anyone else sence this one guy. And then the Dr asked Him and that's when it came out. She understood why he thought it was dormant. And trusted him enough to know he wasn't cheating on her. But they had to go through a lot to get to that point. But the funny thing is she said oh well I have it now so they didn't need to use condoms. and now they have been married for over 12 years.
I guess what I am saying is you don't want him to have a problem then accuse you of cheating. That would really suck!!! Oh and by the way that person is me. Ok I am out of the closet now too. Damn i can't lie to you people! Anyway. My outbreaks where bad in the begining and have calmed down quite a bit. But please tell him so you don't have to go through what I did. And i was using kind words when the dr asked who I had shared myself with. She was a little more rude then that. We never went back to her. And my husband and I are going on 20 years with eachother by the way.