What Causes Clear White Vaginal Discharge And Back Pain During Pregnancy?

Hello. I m 18 and I am around 26 weeks pregnant. A week ago I started having a clear/white discharge that looks like mucus mainly in the morning along with or right before I urinate for the first time after waking up. Three nights from tonight I began having middle back pain. The back pain will come and go. It hurts for about 5-7 minutes then goes away for about 10-20 minutes and returns and follows this pattern all night, but eases off some during the day as I m up walking around and all. The more I walk the less pain I feel. This back pain mainly comes at night, starting around 5-8pm and lasting all night. Last night my face began to tingle, almost as if it were going to sleep. Also today I started feeling some pressure In my lower stomach. I called the doctor 3 nights ago and they adviced me to take tylenol and lay on a heating pad for my back, which only helped for about a hour and then the pain came back. I m concerned because I have a history of kidney infections, bladder infections, uti s, and I also had a miscarriage a year ago and kidney stones shortly after the miscarriage. What is causing all of my discomfort and should I call my doctor or go to the hospital? Is there any real reason to worry?