If I have a child with O negative blood and I am A positive would the father have to be O negative as well

No, The could be A, B or 0

Blood Types | American Red Cross

Blood type doesn't go by genetics necessarily. It's about you, yourself. So it's impossible to calculate you blood type from other family members :D

Keeks 143, blood type is inherited.

Where did you read it's not, that it's spontaneous (or something)?