Suggest Remedies For Irregular Periods

Hello, im 17 years of age and started my periods at the age of 11/12, since then my periods have never been regular and never arrive on the same date, now this is getting out of hand as i sometimes miss 2 months and come on a totally different date. I'm concerned about what may be wrong with myself, also my mum is very worried. Could this be an ovarian cyst by any chance? Will i be able to conceive when i'm older? When i went to my doctor he said over-time they will become regular again but it has been a few years now and still they are irregular. Please help