Hi, I'm 22 And Have Been Getting Discharge And Itching

Hi, I'm 22 and have been getting discharge and itching for months now. Been treated for bv and thrush but last swab came back clean. The itching comes and goes but I keep getting white discharge, I never used to get it. Doctors says there's nothing wrong as the swab for bv and thrush is clear now but I know there's something wrong. I've also been really constipated the last couple of weeks, don't know if it's linked or not, just want to find out what's wrong. Had all STI checked and they're all clear, not had sex for the last 3 months either. It's really upsetting me.