It is normal to feel this way. I would suggest you read up on the 7 stages of grief after a breakup or divorce. It will help you put things in perspective and be aware of what is to come and where you are at this moment.
I know it is hard to hear but you need to cut off all communication with her. Go "NO CONTACT" for the next 60 days. If you have to see her because of work of anything you just mind your own business and don't obsess with what she is doing if she looks fine or where she is. Of COURSE she will try her best to look her best and put on a smile to make sure you see her this way. So you have to not look and put on your own smile and best face. You are happy and moving on like SHE asked you to do.
It is a stupid game and it is childish I know. But it is the only way. You will both put on a brave face and mask. But have comfort in the fact that you know she is doing the same thing you are doing.
Buddy, move on.... Keep moving forward and don't look for her and don't fall into obsession. It will lead down a very nasty hole which is impossible to get out of. Trust me I have been there. This is the time to grieve but also the time to work on YOU and worry about YOU.
It is easier if you don't have children and are not going through a divorce like most of us have gone through. So take that extra time we don't have and use it. Join a gym and rip your body into the most amazing body you have ever had. Read. Learn a new trade.....
Read some of my previous posts and find some of the things you can be doing to improve yourself. Change your habits into positive ones and try your best to keep a positive attitudes.
DO NOT WALLOW IN YOUR SELF PITTY OR DEPRESSION. It is easy to fall into that hole. DON'T
Tell yourself constantly that you are stronger than that and you can do this. I know you can. Just do it.
Be prepared mentally when you see her and have a friend on standby for when it is over. Don't go home and overthink the moment. After work go with a friend and let it out... talk it out. Do not drink any alcohol since it will down you into the ground. Have a healthy meal with your friend(s) then go for a long run and lift some weights. Then go home and pat yourself on the back for having braved the moment and gotten through the day.
PLEASE do this. It will put everything in perspective for you. If you see her then go home and cry you will be putting her as a goddess who deserves your tears and curling up into a ball for and dying for. NOBODY is worth that.
Do things right for YOURSELF. you are worth it.

Good luck buddy

I'm sorry you're going through this. I could relate to you on some aspects. I struggled to not contact my ex boyfriend for a while. But believe me that NO contact really does help. It may not seem like it does or it will but it's soooooo effective. Extremely hard at first but effective. I'm going on 90 days of NO contact and I feel much better than I did in the beginning. My ex boyfriend told me that he did not regret our ending and the reason being was because he was falling out of love and that just shattered me. I've never felt so devastated and rejected, especially when I still had feelings for him. But if your ex doesn't want to be with you I suppose that we can't force them to take us back and be with us after expressing that they don't want to be in a relationship with us. I'm still healing. Yes I will still have sad/bad days more like moments now but I definitely do see progress and I feel so much better.

You can always count on people willing to read and reach out to you here. Do it for as long as you need to. I wish you recovery, you deserve it. Take care. You're not alone.