Hi Mary - Just want to welcome you also. I have UCTD - and am familiar with the pain and fatigue issues, and surely relate to your description of feeling weak, achey and sore, like you're coming down with a cold or the flu. I hope you are staying out of the sun and using sun block all the time!
Like Fran said, probably a good idea to check in with your doctor about feeling so bad. There are others on here with MCTD - I'm sure they'll be along to help. Glad you found this forum - it's a great place to ask questions and feel understood.
Lucy