During my first pregnancy my doctor forgot to give me a rhogam shot at 28 weeks.?

After I had my son, I received a rhogam shot. When I came in for my 6 week checkup he said he forgot to give me a rhogam shot at 28 weeks and I would have to come back several weeks later for a blood test. My blood type is AB- and my husbands is a positive. I came back and got the blood test, it showed up positive for antibodies. He told me to come back in a couple weeks and get another blood test. I got a phone call saying the test came back normal. My son is now ten months. I took a pregnancy test and it came back positive, four days later it looks like I am no longer pregnant. I am wondering if the lack of the rhogam shot during my first pregnancy could have affected this one. Any help, thanks.