I really want to move on but still I can't forget how she betrayed with me?

I am completely broken. I've with this girl for 5 years and she just ditched me within a minute to get better guy than me. I have tried to move on and get started with new life but its seems impossible...I can't shake the pain she gave me...I can't believe she is with a new guy? I talked to my close friends for thousands of time but nothing is working...I am trying to keep myself busy but in the middle of the night I wake up and I can't sleep again. I used to go to a mental doctor but he provides me medicine and now that even doesn't work even.. I truly want to forgive and forget about the past but something is wrong that holds me to not to move. What else should I do???? Its been a year she ditched me..plz plz plz I need help so badly...nothing is working...