Missed period for six months?

I am 20 years old. i had my period in august of last year. i did not have it again until february. i have had spotting every once in awhile. but it doesnt look like blood. it is a light pink color and looks mucusey. and it only lasts for about a day. what could be causing this? i am trying to get pregnant and i know it is not pregnancy i have taken many tests. could i be infertile? or going through early menopause?