Pregnant but he refuses to take responsibility

UPDATE 2! So not even a week after he decided to dump me, over text mind you, my child's lovely father decided to go spend nearly all of his money at the bar, before going to a hotel with some chick. He refused to put the $400 in my account he promised and he's been telling some girl he supposedly hates about our relationship. This chick being the same one he went to the bar with last night. Makes me stop and wonder why I fell for him, why I wanted a family with him when he can go sleep around while I sit at home making sure our child and I are healthy. Im done with him being a child and I'm ready to live my life as a happy single mom. And I hope all you Mama's, single or not, understand everything I'm going through.

UPDATE! He has decided to start bashing me on social media, posting shit like "The party is still going without you, and it's brighter already" and "Nobody ever tells you that following your heart can actually free you". It's all coming from a 22 year old "man". Happy to know that I'm only a year younger than him and being more mature in this situation.

So I'm 13 weeks pregnant and was with my, now ex, boyfriend up until yesterday. Well he sent me a text saying that the math doesn't add up and I am too far along for it to be his. I tried explaining that it goes by LMP but he just wouldn't listen. He packed all of his stuff and left, refusing to admit that the baby is his. I'm really upset because I thought he was excited too and we had talked about getting married. It crushed me and I spent most of yesterday crying. He told me he couldn't do it anymore and that he'd been thinking about it for a month now. I just don't know what I should do, I'm so excited to be a mom I just expected us to be a family. How did you ladies get over something like that? I truly loved and still love him, but I know we aren't going to be getting back together.