I have high blood pressure but my midwife says I am ok for the birth center. What should I do?

See a perinatologist. See a perinatologist (high risk OB specialist) for a second opinion. Your baby is worth it - and so are you.
I'm aprehensive... Birthing centers are ok for completely uncomplicated births (although I must confess I am more in favor of hospitals which can handle anything that may occur during birth). In your case, what happens if your blood pressure shoots up during the stress on childbirth and you need medication to prevent stroke/problems. These things in some instances can affect baby, and then you need immediate assist.