ttc on metformin

Hey ladies, I have been on Metformin for almost 4 months now and still have long cycles (42-50 days long). My dr upped my dosage to 3 times a day about a month ago but still getting bfn. How long did it take to regulate your cycles? my hubby and I have been trying to conceive for 16 months now and its becoming stressful. any advice will help!