Blood type question!!! I don't know what's true or false

So I've been told that a baby has to have the mother's or father's blood type. Which all my children but 1 have their father's the one that doesn't has mine. Yet my mother and someone who I thought was my father have A+ and I have A-. I know my mother is my mother since she got pregnant and gave birth. I flat out asked her "Who else did you fuck"?😂 Is it possible that he is actually my bio-father?