ok, don't know much about American laws
I'm canadian and something similar happened to a cousin of mine.
Her boss knew she was pregnant and they had hired this woman to take over for her while she was on mat leave. my cousin was in charge of training this woman her position so that she knew what to do when my cousin was away. I forget exactly when, but a few months before she was to start her mat leave, they laid her off. the difference is, she had proof that it was due to her being pregnant. It took YEARS in court to finally get her settlement and it wasn't anything close to what she "should" have gotten (according to her) - she said it was not worth her time going through all that, but was glad she got SOME compensation. She didn't see any money until her son was about 5 yrs old.
In canada, when you apply for unemployment (here it's called employment insurance - EI), you boss sends you a ROE (record of employment) with a reason for your departure. If you were fired for no just reason, and through no fault of your own (like, you didn't steal, breach any contracts etc), then you qualify for EI (which is about 55% here)
so what is your boss saying? did she/he just say "we have to let you go and I can't tell you why?" do you get any record of your employment? I'm sure you must have some sort of labor laws or labor relations board you can go to to file a complaint?