I need help!!!

I have had no period for a month and a week now I've taken dollar pee test and they have all came back negative I'm not stressed out either Idk what's goin on I'm only 20 I've had a miscarriage before about a year ago my period were irregular but they would always come around the 24 to the 1st then in June my periods started on the 24th to the 1st and July I didn't have anything and August I had light spotting didn't last long at all I would say like 5 mins and it happened on the 6 and then the 8th I have not had anything since then can anyone give me ideas of what's going on I've been to the Dr but they do not help me they have me take a pee test there too