For Irregular Periods Problem

i m 28 yr married women. last year i got married. i dont have children. my problem for irregular periods, in a month of april 2015 i got periods in two times in a month and after that i consult to doctor bcoz my periods is not regular and two times in a month so she suggest me KRIMSON 35 medicine. she said u take 5th days of your periods to till 21 days than stop than period will come so take from 5th days to 21 days. doctor also done thyroid test its negative in my case. in may & june months my period is regular and i took medicine also. June 23rd is my last period date but after that 6th july (yesterday) my period started. its very low periods like 5th-6th days periods. so please suggest me what can i do.