vaginal pain - negative STD test!!

So a few months ago I started having a lot of pain in my vagina when I was having sex. I was able to get super wet and stay wet, but I tightened up a lot and it caused a lot of pain. This has been happening for a while and causes a lot of friction burn for me and my bf (no condoms.. oops!) well I got tested for an STD and they also tested for herpes because my vaginal area looked pretty irritated and it came back negative. I'm definitely going back to ask them about this odd pain during sex but in the mean time-- any thoughts on what it could be? Confused as to why I'm so wet but it hurts so badly.