Never take a therapist's advice about the way to talk to an employer, b/c this is what happens.

The best way to get your 40 hours a week schedule back, is to go back to your manager and tell him/her that while you appreciate the accommdated schedule change, you still would like to work 40 hours a week. You don't need to be confrontational about it. Just earnest.

You: "Hi Manager Name, thanks so much for accommodating my sleep and anxiety issues that I let you know about, but I see you decreased my hours for the next two weeks. I still need to work 40 hours a week. I just wanted to let you know. Thanks so much."

Something like that. You don't need to sue your manager. But, next time, don't tell your manager WHY you need your hours changed. Just be vague: "I need to come in later in the mornings on my shifts. I can start at 10 a.m. etc"