Conceiving on Metformin

I was just wondering if being on Metformin helped you conceive faster? I'm asking because I got pregnant a few weeks after I started taking it and when I went to my Dr yesterday she was shocked that it happened so quickly. She even said "I can't believe you got pregnant on metformin" Which is confusing to me because I thought the purpose of taking metformin while having pcos was to help you to ovulate regularly, so that seems like it would help get prego faster. I'm confused? lol