Is it too late to file a disability discrimination after accepting a lateral move?

I have epilepsy but I hadn't had a seizure in almost 3 years. In the past, my employer provided someone to drive me for the 6 months that I was without a drivers license. After a seizure at work, HR told my supervisor's boss's boss that it was an essential function for me to drive and a driver wouldn't be provided. I put in for an accommodation to have a driver for 6 months and HR sat on it. The only solution they wanted to look at was transferring me to a different unit (for which I had to compete). If a position couldn't be found, they stated I would be given disability termination. I had applied for 3 promotions and a lateral move to a job with with less travel requirements. All 3 promotions were given to others. My supervisor told me that HR said I wasn't qualified and wouldn't score my interview. I was one of the top candidate for all 3 promotions. After pressure, I accepted the lateral move and have since been promoted (at least pay wise) to a position with less responsibility. This all happened within the past year. Is it too late to file a discrimination suit because I accepted the lateral position? If it's not, would filing hurt a real promotional opportunity?