Treatment For Back Pain And Irregular Periods

I am experiencing bleeding and cramps but had my period 2 weeks ago. There is no possibility I am pregnant. Went to my dr. today and he said that I should just forget I had my period 2 weeks ago and treat this like one. But I don't feel right. I usually have 1 heavy day of bleeding and I have been doing this for 2 days now and am having pain in my lower back. Should I go to the ER? I just turned 33 and the only medical issues I have had are with cysts. I am really freaking out.