Do I have a discrimination case?

I'm a manager of a high vol. retail store. My DM fired me for supposedly knowing I had 2 employees who worked off the clock when they arrived early while waiting for their shift to start. Most of my employees take the city bus to work. 6 out of 7 people interviewed (myself, four assistant managers, and the two hourly employees in question) stated no one knew they worked off the clock. The 1 who stated I knew and the other assts knew is the assist mngr who was placed at my store to find a way to get me fired. I felt my DM was out to find a way to fire me immediately after I was told I was unable to get promoted to DM in training (early Oct) b/c the region still had one DM in training needing to be placed-by company policy the region would not receive more DM in training positions for another year. 6 out of 7 were fired. My DM also did not like that myself and other 3 assts had been complaining abt the low # of hours store rec'd as it did not allow us to take lunch breaks b/c no coverage