Weight gain is often a problem for FM patients.  Here's an article that explains why and give some suggestions that might help:  Fibromyalgia and Weight Gain

As for the pain, you don't mention which medications, if any, you take or have tried.  Since one of the more common side effects of Lyrica is weight gain, you might want to avoid trying it.  The other two medications which are FDA approved for treating FM are Cymbalta and Savella.  Personally, I take tramadol for the pain and it helps me a great deal.  Of course, everyone is different and each of us responds to medications differently.  Unfortunatley, most of us have to try several different things before finding what works best for us.  Some people with FM find that opioid medications like hydrocodone help them with the pain, but it's a lot harder to find a doctor who is willing to prescribe opioids for FM. 

Actually exercise is something that can help with both the pain and weight problems, but you have to be careful, starting very slowly and increasing very gradually to avoid a flare.  Here's some info on that that might be helpful:  Fibromyalgia and Exercise