i found out i had it a couple days ago. I know I got it from my bf b/c I've never been with anyone before him. We have been together 10 months. 2 months ago i noticed he had cold sores on his mouth but he said they were boils. I believed him so I let him go down on me. He was going down on me like 2 months into our relationship and had passed AIDS and STd tests right when we started going out 10 mos ago. Has he cheated on me sometime during our relationship? Why is this all surfacing now? Could he have gotten this from a partner 3 years ago but didnt know about it until now? Do StD tests not show herpes? wtf?

Herpes tests aren't included in the usual run of STD tests. You have to ask for it specifically. A normal run of tests includes syphilis, gonorrhea and chlamydia. So he may not have cheated on you, he just wasn't ever tested for it and didn't ever think of his boils as possibly being herpes.