Can I sue my former employer?

I know this may be a little far fetched, but I was fired from my job for no real reason a couple years ago. At the time I was six months pregnant and the mangers were giving me a hard time. They wanted me to pick up heavy boxes do loads and work my department with no help. When I reminded them that I was pregnant they told me that I had to get a note from my doctor. So I got the note and the manger didn't even take one look at it when I tried to give it too him. There has been tons of other incidents that has happened (too many to list) Well anyway its been about two years since I've worked for them and since losing that job I've been suffering from financial hardship and I was wondering if I could sue? (I need real advice so please answer if you can be of help, thanks)