What Causes Frequent And Heavy Periods?

Hi doctor on the17th August I was on my period for a week, I had went to the doctor on friday the 13th august as the day previous I was changing my sanitry towel every hour, he advised me to get a full blood count taken from the nurse, I phone the doctor back a week later on 20th August and my blood levels came back normal. A week after that on the 24 th august I started my period again it lasted till Saturday the 28th august and then on tuesday 7th september I experienced brown spotting it only lasted an hour. I have been having unprotected sex for the past year as my partner and I are planning for a baby I was wondering if you could give me any advice please.