Herpes: did my boyfriend cheat?

So I went to my gynecologist the other day for a regular exam and what I thought was an ingrown hair on my vagina turned out to be a herpe. I found out I have HSV 1 (but it’s on my vagina- and I’ve never had a cold sore on my mouth). What is fucked up is the nurse said it’s new in my system because the culture result for it came back positive and the blood work for it came back negative. I’ve been with the same guy for 4 years. Can he kiss me on the mouth but then I get an outbreak on my vagina? We have a regular sex life (a few times a week and we don’t use protection) but we both haven’t gone down on each other in a few months. So I’m wondering if this means he cheated??? So I was told that either he had sex or had a blowjob from someone with HSV 1 and then had sex with me which is how I got it. Also wondering how long this has to be in your system for it to show up positive in the blood work?