I don't know whether this will help or not, but my mom (not a PALS) was having trouble of a similar nature, and she was told she needed to drink juices, not just water, as medication she was on was depleting her potassium.
Otherwise, maybe it is time to ask your doctor about it to determine if there is a more serious underlying problem.
ALS is an illness that keeps coming up with new surprises, so sometimes you have to get another appointment sooner than you thought you might need to. Don't be reluctant to go in and get what you need at any stage of the illness.