How to get over him for good?

Luke and I have had a lot of history together, most of which were drunken mistakes (well he cled them as that). We've arranged to be friends, even though I find it hard. I've recently learnt that he's seeing someone else, and that they're having on a regular basis. It's really hard for me. Ever since he's started seeing her, he's turned into a complete . Last night when we were out, he was showing me pictures of her and saying "look how hot she is, I'm shagging her". It was so hard for me, because he was obviously doing it to upset me. Then later on after a few drinks, he said to one of our friends who I've also been romantically involved with "I can't believe we got with her!" I'm so embarred, and I feel like I'm not a patch on the new girl. What do I do? :(