Grieving over terrible breakup-left for someone else and can't go "No contact"

I am writing to get some advice on how to handle this emotionally painful experience I have been going through. My ex boyfriend of two and a half years left me for someone else after we got into an argument. What is even worse is that we are both teachers in the school and see each other regularly. I am 28 and he is 33...
We had an overall strong relationship (so I thought), we both had been through a lot together, and I loved him very much, and was made to believe that he did too. I noticed that he started drifting away the week before we broke up, and he basically told me we were done after an argument we both had. I later find out that he slept with this new woman the week that he became distant. I had to find out by asking around, and going through his email. He gave me no real explanation and told me that he cared about me but at the end he "wasnt feeling it and we were too different". After years of my life that is the only explanation I received and he has told me to stop contacting him. Its been almost 3 months and I cannot seem to get over the betrayal. A lot of the pain comes from the fact that he told me that if he "learned anything from our relationship, its to not speak to other woman no matter what the circumstances are"-indicating that he is in an exclusive relationship with this other person that he values more than me. In addition, he blamed me going through his email as the final straw that pushed him to her. In actuality, he cheated on me the day before and I checked his email because I had a gut feeling something wasnt right. I'm angry at his denial and refusal to take accountability. I can only imagine what he tells coworkers why we broke up.
This makes me feel so used and discarded. He literally replaced me with this new woman and seems to be valuing and respecting her more because they "clicked"(both sports fans?!). I feel so used, like nothing over the years mattered until someone more suitable for him came along.
What hurts the most is that him and I dated for about a year before we became exclusive (which lasted about a year and half) and now he is automatically with this woman that he has replaced me with-and seems to treat her better than he treated me. I do not know how to stop comparing, and how to stop being so angry. I see him at work and know that I still love him, but have mixed feelings of anger as well. Each time I go into work its like reopening the wound. Is it possible that he has truly found his match and I just have to deal? or did he just never love me to begin with? Is he just idealizing the beginning of the relationship and destined to do the same to her? It hurts to think of him finding his better match while im stuck picking up the pieces of a relationship I thought was strong. I just can't seem to move past him and has new woman-when the breakup itself is still fresh to me. I need advice on how to stop idealizing their relationship.
I know that I need to focus on me, but I'm having a very difficult time letting go and not obsessing. I have been seeing a therapist but I need more perspectives on how to stop hurting over someone who left me for someone else that he is treating better than me--especially when no contact isnt much of an option. Any advice? Perhaps something to think of when I see him at work? Thank you!

Hi psychfan,
I'm so sorry this happened to you. I went through a similar experience 4 months ago and am still struggling with it. Like you, I can't go completely no contact because I work with the guy. My guy got married to his new woman right away. So like you said, each day I go into work the wound is re-opened. I feel used and betrayed and humiliated. I have made a no contact policy for myself meaning that I have no communication with him other than that which is required to do my job. Talking about it with friends has helped. Not all of my friends understand how I feel, so I don't talk about with the one's who don't get it. I don't know if I have any good advice for you. I can tell you that it will become easier with time to cope. I can tell you, as some small consolation, that most likely he will do to this new woman what he did to you. You do need to deal, accept that it is over, and move on. He probably did love you but the love has flamed out. It's over. Give yourself time to grieve the end of your relationship and then as soon as you are able, try to focus your efforts on meeting someone new. It's hard. I have fantasies of my guy coming back to me and telling me he made a mistake. He's married for God's sake and I still have this fantasy. I feel crazy. Not sure if this is reply is at all helpful.