Whether you are entitled to overtime depends on the type of work you perform. Generally speaking most people are. I suggest you speak with an experienced employment attorney to discuss you legal options.
As of right now, I do not see a legal claim. I agree with the above posting, you should try to get a doctor's note and see if you can take a few days off to hope this dies down. Your employer only cares about getting the work done.
An employer cannot discriminate based upon pregnancy. However, if she cannot perform the essential functions of the job, the employer may have options. I suggest you consult with an attorney to discuss in more detail and go over all of your options.
It can sometimes be difficult to determine the "real reason." If you suspect your termination is discriminatory, I suggest you consult with a local attorney in order to go over the details and determine if you have a claim.
More facts are needed to answer your question, but generally speaking if you were treated differently because of your national origin that could well be employment discrimination. I suggest you consult with an experienced employment attorney.
More information is needed to properly answer you question. If they are offering money as part of the severance agreement, you may not be able to qualify for unemployment. If they are not offering money, you should, but there is no reason to sign the agreement. I suggest you consult with an experienced employment attorney before signing the severance agreement.