Pregnancy discrimination or fairly fired?

So I've worked at a local grocery store for the past 5 and 1/2 years now. About a year ago a manager (Joe) transfered to my store to take over for another manager that was leaving. Joe never seemed to like me very much because I asked off for the weekends a lot because of it clashing with my husbands work schedule and us needing a babysitter for our daughter. People at work have told me that Joe thinks i'm prissy for needing weekends off, plus i just get that vibe whenever there is a company meeting or anytime i have to work around him. I am currently 38 weeks pregnant and I was about to have a paid maternity leave for 6 weeks. So this is where i want opinions on if people think this seems like pregnancy discrimination or if the manager had the right to fire me... I always work the late shift and our store closes at 1am. The closing cashiers have to stay from 1am to 2am to clean up registers and try to finish up returns. Someone always stays the extra hour with me after the store closes, but this one night, my helper called in sick. So this night after 1am, i started putting away some returns and I ped by something in the aisle that I remembered that i needed to buy, so i put it in the basket. When i finished doing all of the returns, i went to the front and asked an overnight employee in bakery to come be my witness that I was going to get an item. We went to my register and i ped through what I needed to buy. I gave the other employee my credit card, and she finished the transaction by swiping it and signing my name for me. The next day when i went to work, Joe called me into his office to let me know i was being suspended from work for being my own cashier. He told me that he viewed the video and the reciept, and that nothing was wrong with the transaction, but i still could not be my own cashier. He asked me to call him the next day to see what HR was going to do with me, and the next day that i called, he told me i was terminated. Come to find out when i spoke with HR myself, the manager declined to ever tell them that i had someone finish the transaction for me, and he also told them that he asked me to go into the store to sign termination papers, but that i refused. Which is COMPLETELY false. He never asked me to go into the store, which i thought was rather odd... Does this seem fair?? I feel so hopeless now because I never expected this and its not like i can go search for a new job being 2 weeks away from my due date. Any opinions??