<human>: In April of this year my ex cheated on me with a girl at his university after repeatedly crossing boundaries in their 'friendship.' I took him back but after several shitty months and slow deterioration of the relationship we ended it somewhat mutually. 

I was beginning to want to be single and free, and he was tired of my trust issues stopping him making friends with girls. While he was distraught at first, two days later he was chatting up a girl he met online. We had initially agreed to keep contact as we wanted to be friends but about half a week later he suddenly dropped contact. 

Yesterday morning I woke up and saw on facebook he was in a new relationship, with the girl he met online. They met on omegle and she lives in Ireland – we live in Australia. They have known each other barely 3 weeks and have never met in person.

I couldn't believe it and spent the whole day crying or on the verge of tears. He was much more against the relationship ending than me and talked about how he was still in love and would be very hurt if I got with anyone else. But then he's getting into a new, weird online relationship without even giving me any warning. 

It hurts a lot and I can't wrap my head around it. While I definitely needed the reminder that he's changed into a completely different person and the guy I fell for is completely dead, I can't cope with him being so callous. 

How do I move on and get him out of my head? It hurts so much that me and my feelings mean nothing to him anymore, so soon after the relationship ended. I really thought he was different.

 I cant cope with two and a half years of my life being ruined by him. I hate that he absolutely destroyed my happy memories, my ability to trust and my self esteem, and I'm the one suffering while he moves on so easily.

Could you distill the essence of the text into 1-3 sentences?
<bot>: ex from 2 1/2 year relationship is in a new relationship 3 weeks after it ended. I can't cope.