I have PCOS and was diagnosed by a scan when I was 17 and told I'd need help to conceive, I now have an almost 3 year old and a 15 month old
My daughter (eldest) wasn't actually planned, but I fell pregnant with her after switching to a very low GI diet and losing a lot of weight by doing so, previously I'd go months and months between periods, but changing my diet dramatically and losing weight really seemed to kick start my ovaries, and I then fell with my son when she was 10 months old, on the first night of trying, (again after losing the baby weight from number 1) after assuming it would take much longer due to PCOS so starting trying for number 2 earlier than I ideally wanted to!
Since having my son my periods haven't returned (I am still breastfeeding but would still have expected them to return by now) and I suspect it's because my diet is poor again and I'm about 4 stone heavier than I was pre-babies, so for me diet, and weight loss is most definitely the key to my fertility.