it does sound like it could be progression....but...
i wonder, have you been seen by your dr? it sounds like you might need some intervention. or at the least to dx what's happening now.

have you ever had steroids? maybe an OT/PT consult could help give you some more strength or tips for doing daily things like write and sitting up. i wonder if there are any aids that might help you.

you could also try calling your local MS society. they might be able to help.
please reach out to your dr. and, have you had a recent visit to an opthalmologist to check your eyes?

keep up posted. if you had a chair with arms would it help you. or a pillow behind your back?