Can my employer require a doctors slip for every FMLA absence?

I have an approved FMLA claim for a lifelong illness covering myself and a seperate one covering my spouse. In both cases, I was approved for one day of FMLA leave per week (totaling 2 days a week). Now when I take a day off for FMLA, my employer is requiring that I provide a doctors slip for that day. Is this a legal request? I know for a fact it is not the same for all employees. I have spoke with other employees in the company and they are not being asked to provide this. From my understanding, the employer is only allowed to request recertification every six months, and by requiring further medical proof of my fmla, they are in fact asking me to recertify every time I request leave. \ ADDED JUNE 30 /// To clarify, I have one FMLA int. leave detailing my own serious health issues allowing me upto one day a week and an additional case allowing upto one day a week. Yes this totals more than the allowed amount, so I can not take days off all the time. My leave forms are not filled out as being for doctors follow-ups or therapy and such, simply as needed to help care for my spouse and when I have flare ups of my medical problems. As of two days ago, I was officially notified that I am suspended pending termination. Hopefully I can get this taken care of soon.