i am a 28 yr old woman, single...my periods typically last for 36 days.on sep 1 i got my normal periods which lasted for 4 days...but on sep14.i again start bleeding and it again lasted for 4 days ...then on 13 oct...after 30 days i again menstruate...i am worried...during this month i have noticed hyper pigmentation on my face,,,what is the problem