I apologize for posting this here. I do not know a better place to ask.

I was tested prenatally for my RH, I was RH minus.

My birth certificate says I was A +

I was tested when I entered school, I was B. They did not check RH.

When I later studied biology, one of our lab experiments was to test our own blood. I might have performed the test incorrectly, but it indicated little to no response to either type A or type B.

I do not understand. Are there possible explanations for this?