I am sorry for how you feel and what you’re going through, man.
I found out, the hard way of course, that unhealed break-ups show on our faces, especially if we truly loved our partners.
Please know that the more you believe what she said, the more you will be hurt and you will be in ruins for a long time before you start to heal.
She probably has more issues than you do, because for someone to want to hurt anyone like that, they have to be very weak. And she is.
All you have to do now is nurse your wounds and give them time to heel. Don’t jump into rebounds. They will mess you up and you will hurt someone in the way.
Make a list of goals you want to achieve and work on them. A step by step process. Spend more time exercising, focus on your work, and find something you like and make it a hobby. Keep busy to the point that you go to sleep the minute you put your head on the pillow.
Write a long letter that expresses all your pain and burn it down.