What is my ex thinking?

Me and my ex were together best part of 1 year, long story short got new group of friends and one girl stood out to him. She snapped him and liked everything on social media. I announced I was pregnant and he freaked out big time and started dating her not to mention she's 17 And he's coming 23! He's got her all over social media, pics, Facebook official the lot buys her underwear&flowers etc. But still contacts me every week or so. He met up with me the other night and asked to get back together and raise the baby together that he was sorry and she was nothing like me he compared everything she did to me and then said he'd need time to leave her? I couldn't take this as she knows I'm pregnant with his baby and still sleeps with him! His family are embarrassed for him and think he'll regret it when it wears off with new girl. I told him he either ended it that night or we were done for good so I could move on and he told me he was not going to end it with her that night and if I didn't want to talk to him during this on my head be it and just to text him with updates on baby. But no doubt will text or call a couple weeks down line again. He's been with her just over 2 months and is with her 24/7 I've been told. Will he ever regret this? He's never went longer than 2 weeks without texting or calling from blocked numbers again? Please help?
What is my ex thinking?
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