Fired While Pregnant In Illinois

I worked in a car dealership as an internet sales specialist. Today, I was let go due to “performance over the last 4 months” when my job is based on incoming leads and whether we have any good ones or not. I come to work, do my job to the best of my ability and go home. I have missed days due to illness caused by my pregnancy, however when I brought that up I was assured it had nothing to do with attendance and only performance. My job was listed on indeed 2 months ago and when I asked if I had anything to worry about, I was assured it had nothing to do with me and they were only looking for my replacement during my maternity leave.

My MIL thinks I have a wrongful termination case, what do you think?