I'm not speaking from experience or a knowledgeable point of view here; so take this with a grain of salt.
But I would look for a new job if I were you. It sounds like you aren't happy there. If you take action on this at the very least expect for things to get worse, or at worst you will lose your job. They may not have legal grounds to let you go, but that doesn't mean that it won't negatively effect your financial situation. I would expect to lose my job if I took action on this and made sure I was financially sound enough to bear this. If not, wait until you are out of your job. Also make sure you document everything.
And before you do anything, go talk to a lawyer.
For what it's worth, I've been in a pretty shitty work situation for a while and I'll be in a new job on Monday.