My husband had a vasectomy but I’m pregnant ???

Good morning Ya’ll. I had a positive pregnancy test yesterday. Now just to sum it up I got my IUD taken out in February due to recurrent BV but never went on any other form of BC because my husband has a vasectomy. We messed around very often and even close to my ovulation days but I never fell pregnant. I’ve been experiencing some morning sickness and I took a test it came back positive. Surprise surprise MY HUSBAND HAD A VASECTOMY 13 YEARS AGO. He hasn’t had a sperm count since 3 months after the procedure which I just found out. He’s completely in denial about it and says it’s impossible. He doesn’t believe me and thinks I’ve been with someone else but I’ve never cheated on this man. I’m driving myself crazy thinking and being stressed because I know I didn’t sleep with anyone else so??? He says if the test comes back as low sperm count that we have a problem but I didn’t cheat🤔. So I’m thinking if it comes back as low/no sperm count then how does that explain the positive test!?