Dilemma. My girlfriend tested positive to HIV while i negative. Advice Please

My girlfriend of 11 months eloped with me 3 months after getting pregnant. The problem is that after 3 days I figured out that she had genital warts which she claimed she didn’t know about.
We went to get tested for HIV and unfortunately she came out HIV positive while i came out negative. Now it’s been 5 months later and I still tested negative recently.

I now wonder if the baby is mine or should I go for DNA tests or just let both of them go. She claims that she has never slept with anyone else besides me but then she can’t explain how she contracted HIV.
She is a devoted Christian who encouraged me so much to pray and go to church every Sunday, so a part of my heart still trusts her, but I’m now scared of the disease.