What Causes Prolonged Periods?

I am 44 , I was exercising alot , got my period and it last for two weeks . Went to my doctor and she did a pelvic exam , thyroid test and pap test , all normal. My next period started 10 days later and only lasted for 5-6 days. Is there anything I should be concerned about ?

Or just wait and see if my next one is also normal ? I never had a period last that long before or my periods come so quickly together .