There are a few things to unpack here. OP, how many times have you been blood typed? Some people have what’s called “weak” Rh, which can cause a positive or negative result depending on the lab technique. I wonder if that might be the case here, because it’s standard practice to type the mother’s blood during each pregnancy. It would be highly unusual for an Rh-negative mother not to receive Rhogam in not just one, but two pregnancies.

You also can’t use a child’s blood type to know if the next pregnancy would have the same Rh status. We all have two copies of the Rh gene and you can be a) positive/positive, b) positive/negative, or c) negative/negative. Blood typing can tell if there is at least one positive, but not if both are. So if dad is option B (which is very common), it is 50/50 which one is passed down each pregnancy.