I noticed you've mentioned being dx with fibro and i found this for someone else and thought you might find it an interesting read...
Joint issues are technically not caused by MS but if say an MSer has an abnormal gate, it's likely to place additional stress on specific joints eg hip, knee, so it's more of an indirect issue kind of thing. If what you are experiencing is very wide spread (multiple joints) and worse because of the cold weather, I really don't think it is similar to what can happen if it's MS.
I hardly know anything about fibro but i thought fribro caused similar pain and joint issue as arthritis so it could be related and worth discussing it with your GP.
I just wanted to mention I have been having knee pain issues lately. I agree with the above statement about not being directly related. I do have walking isssues andd gait problems because of it. My right foot drags and I limp beccause of it. I am sure in the future I will have hip issues because of my messed up walking lol.
Hope you feel better, it sure is painful, take care