Talk to Gynecologist on Irregular Periods

I am not married. I was having regular periods from many years, sometimes just late for a week or less. But from 3 months i am having irregular periods; skipped the month of March , then periods came on April 9, then next month on May 23 (like 3 weeks late), and now its month of July and i have skipped month of June. but no signs of period. i am not over weight, neither had any problem regarding periods or anything. Need advice . Thanks