Hpv did he cheat?

Me and my boyfriend been together for 8 years got together 10 grade..I recently found out I have hpv..I thought we were each other’s first and only..first kiss first time everything. I keep asking him how do I have it if were each other’s first everything if he keeps telling me that he hasn’t done anything with anyone-else.. idk what to believe because I keep getting told it’s only sexually transmitted and I haven’t messed around and if he “hasn’t” messed around.... he offers to let me go through his phone if I wanted too but how can I get him to tell me the truth or find out the truth,If it’s even true?

We recently just bought a house together like 9 months ago too.. idk what to do..please

Also is it possible to get a false positive hpv test?