Falling for the wrong person

About 9 years ago I fell for a coworker. We started as a casual hangout but I knew I loved him right off the bat. I should mention he had a gf at the time. From then on it was a whirlwind 9 year affair. He had gfs and I was seeing other guys. But it was always him. No one ever compared and no one ever made me feel as comfortable as he did. We know each other inside out. I know what he's going to say before he says it. There is no doubt in my mind that he is my soulmate. I'll think of him and he msgs me, we have the same views, same interests, we know how to push each other's buttons and how to calm each other down. Our connection was beyond physical. Last spring he broke up with the latest gf. He told me he loved me and gave me hope we would soon be together. Sadly there was a tragedy he also witnessed in her family and he tried to be there for her. I understood fully, it was the right thing to do. It messed him up beyond words but he finally came around. He started hanging out with her again but assured me time and time again he was just helping her. This past Friday he came over and everything was great. Today he tells me that night he looked at a house with her that night and bought it with her Saturday. I was floored. I have never been more blindsided and hurt in my life. I am losing my best friend, co-worker who I can always count on to help me out at work and who got me the job I currently have and my lover/soulmate. Did I get what was coming to me? Maybe. Do I know what I did was wrong? Yes. But for the past year I have told him if he was going to date her again I was done. And like an idiot I believed they were just friends. I want to tell her, does she not deserve to know she is going to be living with someone who continuously cheated on her up until the point when they bought a house? I know what you are thinking, and I know I have done many wrongs. I am not looking for judgemental comments. You wouldn't understand my relationship with him unless you were either of us. And trust me I already feel like shit enough for everybody. After all of this he still wants me in his life, as his friend. He says he cares for me and doesn't want me to hate him. I have cut all contact off with him. He surely is a master manipulator.

Do I tell her? Do I let karma do it's thing and just leave it? Getting over this will take years of that. I have to see her at baseball and him at work

I don't know what to do