If you believe you are the victim of pregnancy discrimination you may have a claim. However, you would need to prove that you are being treated badly BECAUSE of your pregnancy.
A boss has the right to be a bad boss, as long as she is not doing so for illegal reasons such as your pregnancy or gender. You also need to consider how much you are being paid. If you could replace this job with another your best bet is to vote with your feet. A discrimination case is a long, expensive and arduous road. If your economic damages are not substantial, it is not worh pursuing. However, if you have a lot of economic damages, you should speak to an attorney or call the EEOC.