Help!

My vagina hurts my bf and I had sex 4 days ago and I was hurt badly, I was swollen for two days now I'm having really thick sticky white discharge, discomfort and itching I think I have an infection but I'm scared I have an STI. We've been together for almost 6 years and I've never cheated on him idk how to ask him for an sti test for us.. can you get these diseases from public bathrooms? Or ANYTHING else?? Its driving me crazy and I haven't slept on days I'm so upset and it hurts please help