First off, I am sorry that you are having to go through this issue. You will get better and I think a new work environment, once you get your mental health back in order, will be a welcome change for you. I am not a mental health professional, but it seems this work environment is serving as a catalyst or driver for the issues that you are having. You do not deserve to have to live in such an environment...you deserve better. For that reason, aside from the legal issues at play here, I think you need to look for a new employer soon.
As to the legal issues...there are two things at play wherein you have legal actions available:
(1) You seem to be undergoing workplace stress and anxiety. You can file a workers compensation claim with your employer for the mental anguish and situation that they have caused your to endure. I think you should speak with your treating physicians about the possibility of filing a stress related workers compensation claim. If granted, it will allow you to take some time off while still receiving compensation. It can later turn into a workers comp settlement for future medicals as well in view of the stress claim; and
(2) I think you also may have an EEOC claim for violation of your civil rights on both gender discrimination as well as disability discrimination. You are being treated differently than female co-workers, which can be indicative of gender discrimination. You are also being ordered to work, even though you are on a mental leave and have provided medical documentation to this effect. A disability is anything that prevents a person from normal life functions. What you are going through would qualify and the treatment you are receiving from your employer would constitute disability discrimination, which is covered under the ADA. I think you need to file an EEOC claim against your employer. The EEOC will investigate the matter and if they find merit, allow you to sue for damages in federal court. You can do this, even if you leave this employer. You must file within 180 days of the most recent act of discrimination.
So, you have two courses of action that you can pursue at the same time against your employer.
Let me know if you have any other questions.
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Best wishes going forward!