I am a male feeling pressured by my employer to take less paternity leave. What should I do?

I informed my employer of my need to take FMLA leave for the birth of my son next month. I have requested 4 weeks as my wife is having as c-section. I have heard second hand through my boss that the HR department is shocked that I need to take that much time off. The head of my HR department told me I need to get a note from my wife's doctor that she will need my help at home for that period of time as part of "standard FMLA paperwork." According to FactSheet #28g from the US department of labor an employer may not ask for certification for leave for a newborn. I feel I am being pressured to take less time off and being discriminated against for being a male requesting extended paternity leave. I did not have to go through any of these hoops for my first child. I have not discussed this further with my employer since I was told I needed to provide a note from my wife's doctor.