Is this a reason to file a lawsuit i need help

I was completely honest about my past already had a background ran on me and they still promoted me 2 years ago but only now it seems it’s an issue but if that is the case then shouldn’t everyone that has a background the same rules apply to them? this may be long I need help.. iv been with my current employer 3 years on may 6,2021, I am a great worker never call out, never late, work overtime , do whatever is ask of me .. I was promoted to a manager within one month of being hired, they requested a background check for the promotion and my gm was made aware of my past and what would come back on the background check “I also put on my application this info too” he replied with “we will take a look when it comes back and go from there”.. well he went ahead and promoted me gave me a raise and then background came back like a month later remind you this was 2019, we sat down and I explained my past to him and he had a meeting with his district manager and they both decided to allow me to be promoted regardless of my background check due to my excellent work I do.. fast forward 2 years later that particular gm was fired about 6 months ago and we have a new gm now, well I recently noticed on our schedules that we print out that beside my name it just has me as a crew member no longer a manger .. even though not one person has ever made me aware of that I also checked and my pay decreased back to crew member pay so I went to the new gm to find out what’s going on .. she said she would find out she wasn’t sure .. well weeks later “iv still been the third shift manager, still been doing all my manager duties etc .. but she comes to me and says that she has the authority to fix my position title and change it back to manager and my pay however they want another background check ran on me and if anything shows up on it I will be terminated ... or .. I can just continue to be a crew member and she would like for me to train a guy that has only been there 9 months to take over my position.. so I’m confused as to why one I could still work there if I have background as a crew member but not a manger .. 2 I’m confused cause I have 2 mist charges NO felonies that was done 6 years ago I understand it looks bad but I have already been punished for those crimes I don’t understand how they could allow me to work there and promote me 2 years ago but now fire me 2 years later with the exact same info that I was hired / promoted on .. also they are other managers that work here also one of them was just released from prison after serving 17 years for murder and they allow him to be a manager also the gm boyfriend is also a manager he has felony meth charges but that isn’t stopping anything I feel like this is wrong and I’m so upset on what I need to do this isn’t right and it’s not fair please help me do I have a case here or what should I do thank you