I'm 20years old I have an irregular periods for last four years I had suggested my doctor. She pescribed gynovit and some vitamin tablets for me but still now I'm having the problem so please suggest me

See your doctor and try something different. There are many hormonal, physical, and psychological reasons for irregular periods and no one online will be able to tell you what it is. Your doctor is your best choice. Maybe look at a birthcontrol, that should steady things unless you're trying to get pregnant.