Consult an employment law attorney ASAP - can locate them on Avvo uner "Find a Lawyer"
This is not intended to be legal advise or as legal representation. I am a California personal injury attorney . Be aware that every state has its own statute of limitations; and statutes & case laws that govern the handling of these matters.
contact a reputable marion county lawyer. if you don't know of one you might try either tom hastings or jack crawford in indy for a recommendation. you may have several things going on: the workers comp case and there is also a bad faith provision in the comp statute; retaliatory discharge because of the wc claim and of course the ADA as pointed out by the other avvo responders. finally if the MVA was caused by someone other than a co-employee or yourself then you have a third-party case. good luck. head injuries can have very serious long-term consequences.