What Causes Pain In Left Side Of The Vagina?

I have this pain in he left side of my vagina. It is only on the inside and is on the wall. It gets really red and hurts during intercourse. After a few days of rest it goes away but comes back. The pain increases each time I have sex. I have only had one sexual partner and he has only had one too (trust me, no cheating has been involved). I was given a shot and antibiotics and it is still occuring. I am scheduling an appointment tomorrow, but it could be months before I can actually get one. Please help!