I was diagnosed with PCOS a few years ago. Just so that we're talking about the same thing: Polycystic Ovarian Syndrome, correct? It did explain my hirsutism (excessive hair, like on your arms) and missing or extremely irregular periods (amenorrhea). It's one of the leading causes of infertility. With PCOS, the affected gland is the pancreas, and you're overproducing insulin. So yes, weight is a big factor -- and a low carb diet will help you get your insulin levels under control, which is probably why your doctor suggested it. I'm on modified Atkins diet and lost about 40 pounds. I eat mostly protein and veggies.
I don't think we're allowed to post URLs here, so go to Google or some search engine and type in PCOS. There's a lot of research out there, and a lot of useful sites.
Some warning signs of PCOS:
irregular or absent periods
ovarian cysts
hirsutism (excess facial and/or body hair)
alopecia (male-pattern hair loss)
obesity
acne
skin tags
brown skin patches, often found in the nape of the neck
high cholesterol
high blood pressure
exhaustion and/or lack of mental alertness
decreased sex drive
excess "male" hormones, such as androgens, DHEAS, or testosterone
infertility
You might also want to see an edocrinologist, to be tested for diabetes (I'm also a diabetic).
Good luck!