My Boyfriends Ex girlfriend may be pregnant by him..

My current boyfriend and I have been together a year. His ex girlfriend texted him recently saying he may be the father of her baby. He told me he wasn't with her the couple days her doctor said she could of gotten pregnant. Although the pics of her baby she has been posting does look like him, and I'm very worried. I love him no matter what but I never thought something like this would happen. He tells me he would never be back with her and I should stop worrying because he loves me. He is now doing a DNA test to find out. I'm not sure how I'd feel if he was a father now. I'd still love him but how would I make the relationship work. This is extremely hard for me, advice anyone please?