I had sex Friday two weeks ago and my period was dued that weekend. I got my period on that Sunday. Usually I have heavy flows but this time I would not have enough blood to fit on a pantliner. Plus my blood was brown which its usually red. I have lower back pain at times and my stomach hurts occasionally. After I eat sometimes I get this feeling I might throw up( my mouth gets watery and I can taste throw up in my thoart). And I have been gassy. I need help I don't know what could be wrong.