PCOS can lead to excess weight, so once you're being treated for PCOS, your weight should stabilise.
Victoria Beckham has PCOS and it hasn't stopped her having children, I believe it only affects fertility if it goes untreated. It does re-occur so if you are actively trying for children you will need to keep up treatement.
I know it's hard to hear when there is something wrong with you, but this really isn't that bad a condition to have. It is treatable, and it's better to know that you have it.
*hug*