Why did my period last for almost 4 weeks?

I'm 17 and have never been sexually active. I started taking a low dose birth control for about 2 months b/c my periods were painful and caused me to get really sick. I stopped taking this almost a year ago due to problems w/ blood pressure. I haven't had my period for about 3 months until a couple of weeks ago. (this is somewhat normal for me though b/c it has always come and gone but my average days that it lasts is normally 6-7). This time when my period started it lasted for almost 4 weeks. When it had gone over two weeks I got really worried and wanted to stop it any way that I could, so I took the low dose birth control for three days but then stopped b/c I got worried it would mess up my blood pressure again. The med did not stop my period at all and I continued to bleed for another two weeks. It has finally stopped, but throughout these four weeks I have gotten many what you would call "hot flashes" and the flow of the period at the beginning was heavy and went to medium before finally today going to barely any thing at all.
Asked Oct 19, 2013

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