hey!! Welcome to the club my friend! I've had PCOS since I was 13. To start off, this disorder has soo many different presentations that it's hard to say which symptoms you will have or which ones will be the ones that bug you the most.
Some girls do have a hard time losing weight, others don't. For example my main issue is facial hair but not so much my weight, even though I also suffer from hypothyroidism. I do think that your doctor jumped the gun a little bit with telling you that you cannot have kids. According to my doctor it is hard to say whether you will have trouble or not until you start trying. He said some women really don't have any issues while others need quite a bit of help to get pregnant and of course, there's the other extreme with women that can't get pregnant at all. The reason for this is that your body doesn't ovulate every month. On a positive note, there are drugs out there to help you out in ovulation, etc. so not all is lost! I know it is hard to get these news when you're older and you have been thinking of having a family for years, but you have to know that there is hope out there! Hell, you might get pregnant on the first try! you really don't know until you try.
If he suggested for you to lose weight, it might have to do with the fact that if you do get pregnant it's safer for you and the baby. Have you tried losing and do you have a hard time?
If you have trouble with losing weight you can get an insulin resistance test. Sometimes women with PCOS that have trouble with their weight have insulin resistance. Mine came out ok but I know it is very common among people with our disorder.
I can't stress enough how important exercise is in balancing your hormones. I find at least that when I exercise regularly my periods are more regular. Also, if you have insulin resistance, it's important to try and eat foods that have a low glicemic index (spellcheck on me here). I also read a while ago that sometimes medication for diabetes helps to balance things out. Just a few things to research because I guess I don't have much info.
I take birth control for my symptoms but birth control is really a mask for symptoms rather than a cure. I will have to come off these, of course, when I want to try and get pregnant. Has your doctor prescribed anything for you?
Just know that you're going to be ok. There's no cure for this but it can definitely be managed. Let me know if you have any other questions!