Why The Menstrual Periods Are Missing?

i havent had my period for a week and 2 days my cycle length is 37 days. i was taking pills to get my period because i was 3 months without getting a period,but my doctor told me to stop because i was getting my period without taking the pill. i took a pregnacy test and it came out negative. i had sex all this month could i be pregnant with a low hcg or i would have to take the pills again