Vaginal pain with white substance inside vulva

I'm 24 and I've had vaginal pain for a few years now. My doctor doesn't know what it is and I was wondering if anyone could help me. I have soreness all the time inside my vagina. I also have a thick white substance inside the vagina accompanied by a foul odor. When I have intercourse it becomes dry and scratchy and I often end up in tears and have to stop. The pain increases when I'm menstruating. There is a certain spot about 3-4 inches inside my vagina on the upper wall that when pressed is extremely painful. It also sometimes hurts to touch my clitoris or event he clitoral hood. I have only had one sexual partner and I don't think it would be an STD. I also have back pain and was wondering if these two conditions could be connected in any way.

Thanks...