How long after starting metformin/glucophage did it take to get pregnant?

My dr. put me on 500mg four a day. I have been taking it for about 2 1/2 months. I was just hoping to get some success stories. I am getting more worried all the time that I will not be able to get pregnant. Dr did more blood work this week and said that it is helping my insulin resistance, and I ovulated on my own. I have been ttc for 3 1/2 years the only other thing that I may be able to afford is the follistim or gonal-f shots.