I have PCOS and Crohns. I also am never underweight - quite the opposite due to the PCOS! The cause of PCOS is insulin resistance - it is important to eat a low glycemic index diet - the challenging part is that this also means trying to eat whole grains, fruits and vegis which is a real challenge when flaring with Crohns - tricky!
Exercising every day is also important to help your body use insulin more effectively. For PCOS some gynos treat with metformin (a diabetic medication) but a side effect of that can be diarrhea! PCOS and Crohns don't play well together
Now for the GOOD news - Although PCOS can cause problems with fertility I have SEVERAL friends with PCOS that have taken medication and then gotten pregnant quickly when they were wanting too - so there is lots of hope in terms of starting a family - start talking to your doctor if you are thinking about
it. And, yes, seeing a gyno to confirm the diagnosis and get treatment options is a good idea.
I have PCOS and Crohns and right now I'm feeling good - remicade for the Crohns and a low GI diet and exercise for the PCOS - may it continue!
Really, do have hope, it really can turn out okay
hugs!