FMLA, I received a written final warning stating that my leave was not approved, days later I get aproval help?

I got approval letter from our home office after my District Manager gave me a written (final) warning. I have been with the Company for 3 1/2 years & have never been wrote up until taken my fmla leave. Since then I have had an additional write up for something that was not relevent. My boss now treats me very disrespectful & I was just wondering is this how fortune 100 companies treat everyone that take FMLA leave? I love my job & have always gave 110 percent but, it seems since I was out those 3 weeks that now they are trying everything they can to terminate me. So is fmla really worth all the trouble it causes?