It sure as heck, sounds like MS to me, Rainbow. I don't think your weight has much to do with your exhaustion, especially if you are used to being heavy. You are a big girl, like me. 5'7" - 180 lbs. It is harder to carry the extra weight around, though.

Diagnosis comes slow sometimes, so, just make sure you get tested for all the nastier stuff, like Brain tumour, ALS, etc... There are worse things than MS.

Take a deep breath and while you wait, get the helpful Meds from your Doc/Neuro and live your life to the fullest of your capabilities. There is no cure but you can maintain it a little better, with proper care.