how can a person just switch off and not care 🤔

i thinks its now been in total about 5/6 weeks my ex has yet to see his daughters. age two and 7 months. and im currently 5 months pregnant. i changed my number 2 weeks ago. but there is MANY other means of contact. besides having my number. (we even both already have solicitors, who are aslo both best friends) he could ring and bave arrangments passed along. if he wanted enough. hes just run off back to his ex and kids. telling her the past 2 years with me was all just a huge mistake and he hates me. and is taking nothing to do with this new baby. like wtf. he even slept witg me 3 times and when i found out he was back with her and i told her. he denied it. he passes me and kids everyday and just dosent care. i dont understand why he isnt mjssing his kids at all and how he could say all that.