My last period was March 16th and ended around the 21st. About a day or 2 before my period ended, my boyfriend and I had sex (protected). And on the day it ended or the day after, I began feeling a pain in my stomach (not uncomfortable really) and slightly less in my back. I looked up the symptoms and it seemed like a Urinary Tract Infection and it told me to drink a lot of water and try and flush it out. I did and it went away. Now it's 2 weeks after my period and I'm seeing very light spotting. Started off red and is now brown. I read it could be due to poor diet (which I was eating poorly during the time I was experiencing the stomach pain). I hadn't excersized in about a week and went on a run yesterday, right after the run is when the blood appeared but it's still here (only a day later but still).