Rheumatoid Arthritis Treatment

I’d like to verify I haven’t been misdiagnosed before pursuing treatment.

For the past several weeks I have had pain in my muscles as well as my joints. I take 10mg of prednisone daily and methotrexate injections once a week for the rheumatoid. For the first time ever, I have had pain in the area of my clavicles today.

A little background: I have been really sick since the birth of my son (17 months ago) and have seen so many doctors. I was finally recommended to a Rheumatologist who thought my symptoms were Sjogren’s Syndrome. I was also tested for Rheumatoid Arthritis but all tests were normal.
Today I had a check up with the Rheumatologist again and he said he thinks it might be fibromyalgia because I have a family history of it. He wasn’t too confident of that diagnosis though so I’m not sure what to think.
Getting to the point: He wanted to put me on Cymbalta but I tried that before and I can’t handle it so he put me on Lexapro. I was on Lexapro after my son was born for Post Partum Depression. Isn’t that just for mental type depression? I mean it isn’t generally used for physical pain is it? He also put me on a muscle relaxer/pain reliever, Movic (I believe that’s what it’s called) so I could get some sleep at night. Has anybody taken these or similar drugs before to treat fibromyalgia? Did you get any relief at all? He also recommended I start physical therapy for some joint pain? Has anybody found success with that?