Guy took back ex over me

Ok people was hoping I could get some helpful advice.. Basically I met this amazing guy and it's been pretty intense as he is only here for a few months and then moves to America. We had been dating for a month and spoke everyday on the phone. Everything was amazing and even though it was early we both had very strong feelings for eachother and saw a future. He went home for a few days and all of a sudden saw his ex out and the next day the decided to give it another go for them and her child (who's not his) after being together 2 years. They mainly broke up as he goes away a lot for work and she hadn't been there for him when he's injured himself they fought quite a bit etc. She had tried to get him back before and he said no. Anyway this was a complete shock for me and I believe him when he said he never i he yes on getting g back. He keeps saying he is sorry and that he has strong feelings for me and misses me and when he was drunk said he loved me. We got together last week and for very close which I'm sure his ex wouldn't be happy about. He feels guilty and and tried to leave things with me on a happy note but he has text few days later asking how I am. Has anyone any tips on what I should respond? He's always moving to the states in a few weeks so even though I know I shouldn't I want to see him before he goes but also play it cool. How can I get him back and make him realise he made the wrong choice? I'm completely devastated x