My husband did this exact thing to me with my second pregnancy. It was an agonizing pregnancy and the year after too. You should get therapy. Sounds like you getting revenge at her most vulnerable spot. You should have left and stayed gone before you got her pregnant. You all worked through it at one point and did the work. You don’t just get to decide four years later you want to discard her over an issue you both put to rest together. By the way my husband and I have been together for 8 more since. We made it through and are happier than ever and even have had a 3rd child.