Can I sue my employer for continue FMLA HARASSMENT?

I’ve been with my job for 23years. I work for the Federal Government. For over 8years I’ve had approved FMLA for a serious Chronic Condition. Had knee replacement at 47years old 2018 and had complications leading to two more surgeries in 2019 on same knee. I have restrictions listed on my FMLA, but management continues to harass me about my FMLA. They’re constantly telling me I don’t have restrictions and telling me I need to bring in documentation. I had a supervisor tell me FMLA is just for leave not for restrictions. I was put out the building for not bringing in documentation for my approved Fmla. Was out for 4days and union told me to come back because management claimed they never put me out the building. Came back to work still without documentation and was allowed to do my job within my restrictions. Every other day I’m being harassed about my FMLA documentation. My manager stated I’m suppose to walk around with my documentation on me at all times. My supervisor told me he was privileged to a conversation with my manager and labor relations about my FMLA. IF I ask a question I’ve been told I can go home if I don’t like it. I’m becoming very stressed! What should I do?