My Dad may not be my father...

I'm about to be 28 years old and I've had issues carrying full term since I started trying 6 years ago, so I've had just about every test you can think of. So I've known for a very long time that my blood type is (AB-). Well so far this pregnancy has been perfectly healthy thank the heavens except a small discrepancy in my bloodwork. They found positive D antibodies. I have a 17 month old daughter that I was blessed with and they never mentioned this with her entire pregnancy (also full of tests and monitoring) so I acquired the D antibodies afterwards. So they want me to see a hematologist, I'm trying not to stress. So I was discussing the situation with my mother and she told me her blood type is (B+). This caught me off guard because I was pretty sure my father was (O+). While two positives can possibly have a negative blood type baby, there is absolutely no way for me to have (AB) if neither of my parents have (A). I asked my father to confirm with his dr about his blood type. I told him I needed it for my hematologist appointment and didnt mentioned my mother's blood type as I dont want to upset him. To make the situation even tougher on me, I hated my father my entire childhood and most of my early adulthood. I only gave him a chance after I lost my daughter Adelaide and I didnt have the energy to hate anyone. He and his wife were supportive during my divorce and my rough pregnancy with my daughter Clementine. I'm now pregnant again and I really dont even know how to handle this. I don't want to break his heart but I've never felt like I belonged in his family. So much of my life would have been different if i had known he wasnt my father. I can't say it would have been better at all but some pretty horrible things would definitely had been avoided. I'm just at a loss and full of so many mixed emotions. I'm angry at my mother and sad for my father. I also haven't discussed this with anyone but my fiance. I honestly don't know what to do 😞