There are a number of avenues of redress available to you, the aggrieved employee. However, whether you use only one avenue, or all avenues, is dependent on the action taken, and the "Serious Health Condition" that you have. Each avenue is presented herein and it will be up to you, the individual, to determine which course of action you will pursue.
Also, understand that you are not limited to only one course of action. For instance, if you file a grievance because of an adverse action on your FMLA request, and you win that grievance, that does not preclude you from filing a civil action in federal court under the FMLA statutes, or an EEO complaint, dependent on the circumstances, under the auspices of EEOC regulations. However, you can't file a civil action in federal court and simultaneously file an EEO complaint, or a complaint with the Department of Labor.
I have also listed yourself as a course of action, per se, because you
are the defense, and the offense. If it is not for you, and your understanding of the circumstances involved, then there can be no
effective defense, or offense. Ignorance, in this instance, is not bliss, nor is apathy. People state that they want the situation
to change. Yet, to change what is wrong you have to stand up for what is right, and be willing to weather the storm until the wrongs are made right.