My question involves labor and employment law for the state of: Texas

I have worked for the company for nine years and a manager. The new boss was hired a year ago and has tied my hands when it comes to purchasing and ordering supplies. He set out on a witch hunt and went to the employees under me and asked if there were any issues with me, to which the replied, yes. We do not have supplies. I reminded him of his directive. There is much more, obviously. I went to the doctor and was given two months of leave under FMLA and the Dr. sent the info to my company. She was in the process of finishing out the FMLA paperwork. Four days later, I received ten phone calls, multiple texts and emails that my boss wanted to talk to me. I called him and he basically said that I was fired or could resign. I told him twice that I could not make a rational decision right now, and that I was under FMLA protection. He said that he had not received the paperwork and I replied that it was being completed by the Dr. He did admit that he received the notice from my doctor that stated I had two months of leave approved. He pressed the issue and I finally said that I would resign.

What are my rights here? I qualify for FMLA because I have met all of the requirements and I do not see how I can be terminated/forced to resign while on FMLA.

Any insight or advice is appreciated!