Burning during sex?

My boyfriend and I frequently have sex, but a few weeks ago it started to hurt and burn after a while. We held off having sex for about 2 weeks and tried again yesterday thinking it was just a small tear or something. When we tried again it felt fine for about 10 minutes and started burning again. We know for sure it’s not any sort of STD, and I don’t believe it is a UTI because it only burns during sex. Anybody have advice before I go see the gyno??