PCOS - What causes Polycystic Ovarian Syndrome (PCOS) and how many women have it?

i am 22 year old girl. i am working witih medical transcription company as a medical transcriptionist since 2 and half years. when i was in 10th i had period first time then it became irregular then i consult with gynechologist one of told me it is hormonal changes so thats i am having irregular period and one another told me the same and advised me for hipnostic treatment and prescribed me to take registrone for 5 day with t.i.d. basis after meal. then again they prior doctors went somewhere out so i went with one another physicican for the same problem she prescribed me to take novalon for 27 days then i got period and advised me to take it for 3 to 3 and half months i took it also but i had not got result which i wanted. then i had intercourse with my spouse and broken verginity then also i didnt have period on regular time. mean while he take me over at another physician she took my sonography and it showed that i am having bulky ovaries with 5 mm of cyst (follical). so i am having that PCOS and she prescribed me glycephage and diabeta twice a day.i mean any of one in these both medication in case one is not available at clinic for 3 to 4 months and i started it since july 2007 then i got period on 23rd of augest and then it came on 9th of octomber and then again in same month 18th of octomber for one day in same month while doing intercourse then again on 25 to 29. then while that time i was taking prescribed medicine and then still now i am not having period on regular base in month of november. yeah i had it on 26 while having sex. please help me out of this problem because that lady who was my gynechologist she went out of town and there wasnt any other gynechologist. please help me out as i need ur help.