Due to pregnancy induced hypertension I was on 3 different hypertension medication post partum - Labetalol, Nifedipine and Propranolol which are all medications that are approved by AAP for use in breastfeeding mothers. I delayed feeding for 3 hours after taking Nifedipine.
If you take your blood pressure frequently and you're noticing it's high that's probably causing you stress and not helping your blood pressure. During my pregnancy I would get very anxious and scared about what my BP reading would be while watching the monitors and machines as the nurse took it every 3 hours (I was on hospital bedrest for the last 3 1/2 months of my pregnancy) that my blood pressure and heart rate would rise. Once they put the machine that the numbers read out behind me, just having it out of sight calmed me down. So I can imagine that if you are checking your blood pressure often and it's high it's likely going to cause you to be more anxious and stressed each time you do it.
I would recommend that you search for an internist who specializes in blood pressure/hypertension. After I delivered my baby my OB referred me to a family practice doctor who wasn't experienced with hypertension medicines (her words) and so she decided that she would just do a trial and error with my medication and when I asked her if they were safe for breastfeeding she was clueless. I didn't even bother getting prescriptions from her. I researched through my insurance company's provider directory and looked through local hospital clinics until I found someone experienced.