You need to suck it up this very minute and go enjoy the day with your kids. Stop letting your emotions control your actions.
When you get some free time after the kids leave you need to find some information on forgiveness and learn to forgive Andy once and for all. Do it for yourself. You deserve it.
Every single person in this world has been hurt. If we all sat around and felt sorry for ourselves and our past pain, we would never be anywhere. Everyone would just sit around trying to get even. There is nothing Andy can say that will make you feel like everything is going to be OK.
You have to start focusing on the future and let go of the past once and for all. The only person you are hurting by holding onto all of this is yourself.
What Andy did was wrong to you? That is a fact! But...You must forgive the hurts from the past and move forward.
There are no guarantees in life. There is no guarantee that he won't hurt you again. But...if he does, you will be OK. Thinking that it is just a matter of time before he hurts you again is a sure way to make it happen.
People hurt people because they have been hurt. Andy hurt you because of something you did to hurt him. Who gives a rat's a$$ who hurt who in the first place. Should he have been the bigger person and stopped the get even cycle--Sure. But he didn't. Now you have the great opportunity of letting it stop with you.
Now suck in those tears, put a smile on your face and do something to shift your mood towards the positive. I'll be thinking about you today and sending you positives vibes. Best wishes!
P.S. As I write this information to you, I am telling it to myself.