What everyone else said.
Go dancing, singing, swimming, boating, fishing, running, Zumba. Go to the beach, or the zoo, or whatever takes your fancy.
Get into martial arts or any other sport where it is ok to beat the crap out of a sparring partner, or take a few hits!
Heal, then live life to the fullest.
Enjoy every morsel of food, wine, deserts. Take a cooking class.
GO LIVE YOUR LIFE. Don't worry, actions always meet consequences.
Not my STBX yet, but every boyfriend I ever was cheated on by was the one missing me in the end. They saw my beautiful face, smiling, loving life, and radiant and looked at the scalawag they screwed around on me with and ....bam. Instant Karma.
Heal first. Then go out and live a wonderful blessed life. Accept that you will have some bad days, and then move on.
Cry when you need to. Honey, get it all out. Get on ADs if you need to and see an IC for as long as you need to.
You were with him through some very formative years, so accept that it is going to hurt and that the hurt is going to be for a while. But you are so young. You have so much more life to live still.
Rearrange your home so that it suits YOU! That is also cathartic and healing!
He is going to get his shit. He already is, he doesn't have you anymore.
You would NEVER knowingly be an OW it is just so low and just downright disgusting, pathetic, and nasty!