Metformin and Irregular Periods: Impact on Ovulation & Cycle Regulation

Question
I am 22 yrs old and I have a very irregular cycle.  During 12 months I only get my menstration about 4 times and the blood is very dark (as if it was old blood) and it is light.  I was put on metformin, 500mg, to try and regulate my sugar levels so I am able to ovulate.  When I was put on metformin I had started a cycle 3 days before (again, old blood).  Because metformin brings down a cycle am I going to get another period in a few days and then ovulate or will this be my cycle and it is safe to assume I am going to ovulate soon?  I don't know the length of my cycles because they don't come around very often.  Also, when my cycle was regular I had long heavy periods and now I don't.  I am not even sure if what I am having is even considered a period.  Now that I think about it I had my "period" on July 25th and I got it again on August 22nd.  Should I use those dates to calculate when I am going to ovulate?  What are the pregnancy success rates w/ Metformin and within how long?  Thank you in advance for your help.  

Answer
You will have to consider your period to have begun on July 25 nd again on August 22. This would give you a 29 day cycle (normal). The Metformin will control any cargohydrate intolerance or diabetes, and will help you to ovulate, but will not change your cycle or "bring down" your period. In order to better regulate your cycle, you may consider going on birth control pills for a few months.