Suggest Remedy For Irregular Periods

I've missed my period before but my OB/GYN said it was just stress. They gave me a pill to take for a week that made me have my period. I'm 16 and I've had my periods since I was about 9 and they still aren't exactly regulated (they will be at the beginning of the month for a few months as then switch and be at the end for a few months) I'm late for it this month but im having all the symptoms of a period, yet there is little blood (light spotting that only lasted a few hours the other day).There is no way I'm pregnant cuz the last time I had sex was months ago and I've taken 2 pregnancy test and both came back negative, but I took a morning after pill after i had sex too and my periods haven't been the same since. I had a period last month though after not having an actual period for a few months after (I think the morning after pill). Is there something wrong with me?