Bleeding after 13 days. This health.

I am not pregnant.I had irregular periods right from puberty.my doctor gave meprate after taking that on 10 day I got period went for some hormonal tests on 2nd day of my period and on 8th went for FS and uterus scan.finally my doctor told everything is good nothing to worry and she told folsafe-L and normoz-DS tab need to take till conception(once in 3 days I will forget to take those) and duphaston from 18th day(anyway I will be taking this from coming Monday ) Finally what I want to know is last month 11th I got period again today I could see bleeding and back pain and stomach pain Not understanding why I got period again it's been 14 days exactly I got my last period Please help me.we are planing for a baby so worrying about this health.