Irregular Periods. Taken Medicine. Irregular Due To Overweight?

If not a problem i would require a reply from doctor Chetna Jain(Gynechologist). I am 26 years old unmarried . It has been from school time my periods were irregular, sometimes in school i used to get it for a month i dont remember if it was due to the gynachologist s medication and sometimes i never used to get it for nearly 6 months in a stretch , once i reached college it was better but still not so regular. I am right now 63 kgs and height is 5.2. since february 2012 i am not getting my periods regularly. i take medicines, and have stopped the medicines currently as they cost a lot n i find no cure.I would like to tell u may be 3-4 years ago when i was 53 kgs i used to get my monthly periods on time, is it irregular as i am fat or are there any other reasons to irregular periods?. kindly help me an let me know each and every reason, As its between you and me i want to tell you i havent had sex at all. Please do reply to all my queries if you would like to ask me anything personal please do ask. I will be waiting for your early reply.