As an employee can I sue because I think my rights where violated since I wasnt able to prove something?

At work, there was a investigation. At first, I thought it was a training or something. Then it when on with some man giving a b.s. life story about himself...blah blah blah...then he asked if I every did anything that caused loss to the company. I said yes, I sold some business coupons on ebay. He said that I took more than $600+ from the company. I told him he was wrong and I could look it up on the phone and show him. He refused for me to get out my phone and threated me that I would have a felony if I didnt sign my name to the restitution charges. His amount included gifts that I put on ebay that I got from my bf, a couple of friends, another employee and very little from myself. Should I get an attorney for this? Not only did he try to say that I took all that but at that amount it makes me look even worse. What can my attorney do for me?