Technically no it aint legal, but it does happen for legal reasons. If your always sick, always not feeling well, always making excuses to not be there, then yeah they can fire you for "being sick". Reading your post it seems like you use to do this, or were doing this in the past.
Just saying if you seriously want to fight this, be prepared for them to look at everytime you called in sick how often you called in sick, all that jazz...
Just saying if you seriously want to fight this, be prepared for them to look at everytime you called in sick how often you called in sick, all that jazz...