Sore Stomach, Sore Back

A few weeks ago I started to get this strange tugging feeling of discomfort in my stomach, directly to the left of my belly button. A few days after this discovery I also started to feel the same sensation on the right side. At first I shrugged it off as indigestion but now it feels as though this light sensation has turned into light pain. I have no idea what it could be. To make matters worse I now have a very sore lower back accompanied by nausea. I went to the hospital a few days ago but the doctor shrugged it off and told me that he believes it is being caused by stress (pregnancy was immediatly ruled out as I am still a virgin). They also took a urine test but seeing as how they have not called me back, it is safe to assume that the tests were inconclusive. The doctor explained to me that pain such as this can often be caused if somebody is really stressed out and that he sees it often. He also perscribed me some tylonal 2 for my back. Since my visit to the hospital, I still feel the EXACT same. I have been really stressed out these past few months with school and family related issues but I do not understand how this pain I am feeling, especially in my back, is being caused by stress. Does anyone have any ideas what this could be? I have the tendency to worry a lot about things like this and I have to admit it makes me nervous that it doesnt seem to be getting better.