Meeting an ex, some difficulties involved

Hi,
Tomorrow I am supposed to go out with some of my friends. Well, today I discovered that my ex is going to be there too.
And I don’t know if I should go.
Like, I think that it’s a great way to “show him what he lost”, but literally I am scared. Because things ended badly. From my point of view definitely.
To give you some background I crated two topics already, he broke up with me for the second time and he cheated.
But for the short review.
He broke up with me in March, saying he needs to be alone and that he’s not ready for a serious relationship (we were together for almost 9 months in that moment).
Then he came back on 17 of April.
Things were great. Like really amazing, I felt loved and we planned a trip together and stuffs like that.
On 21 of May he broke up with me saying that he really cares about me but that he’s not feeling the same as I.
Well.. A ten days later I discovered that from the start of May he was texting with some girl and that he slept with her two days after we broke up. And they are together now.
The girl discovered it because of me and that’s when he texted me. Nothing vulgar or anything but I know that he was angry from the texts.
So, I guess we ended on the bad note.
Everyone is suggesting long no contact and move the hell on, because he acted really badly.
But I still love him. I think about him every day. I don’t know how to stop. I thought that things are going to be easier but they are not.

So.. Should I go tomorrow? Should I talk with him? How am I supposed to act? What if he will show up with her?