Unlimited PTO and Doctors Appointments?

I'm an exempt salaried employee and my company offers unlimited PTO. I'm currently pregnant and have doctors appointments every month. I try to schedule them first thing in the morning so I'm in the office for the late afternoon phone calls. With this in mind, would my employer be able to dock my pay for missed hours due to the prenatal appointments and would I be able to use the unlimited PTO to cover those hours of it came up?

I'm really stressed because my manager is very uptight about my hours and the days I've taken off even though I was a high performer last year. I'm just looking to cover my bases and have different plans in order. Worst case scenario, I plan to dip into FMLA to cover the appointments, but won't be able to until March.