Getting a divorce and TTC

So my soon to be ex and I want another baby together. But he also wants a divorce, he doesn’t want to be in a relationship anymore. He said he only wants one more child and will like it to be with me. When have a 4 1/2 year old daughter together also. We’ve been trying since July, but we separated in December. He still very much wants another baby and so do I. I’m not sure what to do. I mean I will love to have a second child and I know I can handle raising two children on my own. I get disappointed every time I take a test and it comes back negative. Also I know it sounds crazy to still want to have a child and get a divorce. Just looking for positive sound advice.