Lower back and abdominal pain with excessive vaginal discharge

Patient: I have been having lower back and abdominal pain, as well as excessive, thick, yellowish discharge for the past few days (no vaginal bleeding, itching or smell). I thought I might have a UTI, since I was previously diagnosed with one a few months ago and had similar symptoms (but no vaginal discharge last time). I had left over antibiotics (cephalexin 500mg) from last time I was diagnosed, that I resumed taking 3 days ago, but the symptoms are not getting any better. I am married and do not believe this could be caused from an STD or pregnancy. Any ideas of what this could be?