faith, i did something similar in the summer and, like you, even getting to the loo was a major undertaking! had to use the back of a folded up garden chair like a zimmer frame as no way i could get there on my own!
i found that the anti inflammatories didnt really help and after a couple of weeks my doctor prescribed diazapam. i was really, and i mean really, reluctant to take them as i thought of them as "drugs", but i was in so much pain that i did take them in the end and they helped enormously. like others have said, they acted as a muscle relaxant and once the muscles relaxed a bit, things started to settle down. it still took weeks for me to get better (to a degree) but they did at least allow me to move around a bit more freely.
i also found some hypnotherapy relaxation helped as well. sometimes it's hard to relax the body on your own but if you have someone who can take oyu through a guided visualisation it makes a lot of difference.
hope you find something that works for you and you are able to enjoy xmas. mine was in the summer so although i missed weeks and weeks of garden time and riding, it wasnt quite so awful as i think it would be at this time of year.
keep yer chin up doll!
laura