Very fresh breakup venting and advice request

As I type this the wounds of my breakup are still very fresh, only a couple days old. We were together for a little over 2 years. I actually already knew her for years, she was my good friends wife. They split up once he found out she was cheating. After sometime I ran into her randomly and we started hanging out. As it slowly became a thing I had to break my friend the news, which resulted in me losing 2 close friends. I was naive and I thought her and I had such a connection that is was worth losing 2 friends over. The first year of our relationship was bliss, complete happiness seemingly for both of us. I've never felt a connection or love like this. In the beggining we both put 1000% in the relationship. I supported her financially and emotionally as she started her own business after dropping her well paying safer job completely. Her money slowly dwindled and I was there to support her when it ran out. I watched as she dropped long time friends like they were nothing as soon as they didn't align with her way of thinking and ideology, but still reassuring myself our bond was too strong that I would never be given up on or abandoned. Sure enough over time I gave more and more and she gave less. Once we got around the 1.5 - 2 year point her facade finally fell away and I got to see what she was really like. Lazy, entitled, narcissistic, and unwilling to do any significant work on our relationship.

Even as the relationship was crumbling I tried to keep it together and work on our minimal issues. But for her all she cared about was herself, more and more. She eventually told me she needed to be alone and be independent for once in her life. That she couldn't give me the love I deserved and she needed to work on herself. Which normally I would totally respect but I know there was something or someone else behind the scenes Influencing her feelings. I don't know for sure but my gut tells me its another man she was seeing behind my back. I ignored the red flags in the beginning of the relationship, she cheated on her ex husband, and then cheated on her boyfriend she had after the marriage with me. I knew she did this at the time, and the day after we spent our first night together she dumped him.

I truly belive people can change so I gave her the benefit of the doubt, and thought we had something special, and she would not do the same to me, but here I am. Totally heartbroken, feeling used, empty, and betrayed by my own thoughts.

It baffles me that we had such a strong and unique relationship, but she still threw it away and started looking elsewhere for happiness instead trying to put in the minimal work to have a mutually happy relationship. I have already been in 3 other long term relationships that have fallen apart at the 1.5 year point. It is hard not to be pessimistic and think I will never find a true long lasting love. I know better though. I have alot of good things going for me, and I have learned so much being in these relationships. But here I am anyway, barely sleeping, eating, and completely controlled and bombarded with negative thoughts and feelings.

I know for sure this is so fresh and it won't last forever. But if anyone has any advice on how to clear my head of these thoughts and not let them be so debilitating I would really appreciate it. Thanks for reading