I'm 25 Years Old And Unmarried. My Menses Not Regularly

I'm 25 years old and unmarried. my menses not regularly so i to a doctor and take medicine since one year when i take my medicines my periods ok but for one month i stopped my medicine periods are regularly for two months only after that not again i went to doctor she give me injection estogen and progestern then again my periods are regular.she gave me some medicines also. now i changed my doctor she gave me yamini LS but tomorrow i forget to take the medicine so what i do