My heart now has walls. And I don't know what to do.

I was with my ex-girlfriend or 3 years. She kicked me out about 5 minutes ago you moved in other man in. Said that he was a friend she was helping had no job she was supporting him. I found out later that she was paying favors as well. That she cheated on me not too long after getting together, with a person that she said was a friend. And she would always come home late cuz she'd have to stop and see this friend. And a friend that I trust is the one that told me she said she wanted to tell me when she told her but she knew that would break me and she didn't want that but now I'm broken more than ever and I just have no reason to be here anymore I'm not going to do anything stupid but I just don't know how to rebuild myself I gave her my whole heart. She was my everything thought she was mine forever and come to find out she wasn't even mine completely. I bought her a car and she changed after that and then here I am now I just I don't know what to do and apparently since we have been separated she has had three boyfriends possibly 4. Here I am broken and no good to anyone my mental health is crap right now. And I really don't see myself getting into a relationship anytime soon or if ever. I'm just hurt and don't know how to feel I feel like I'll just die alone. Oh and the deal with kicking me out was we needed to work on us and she wanted to stay together while trying to do I still was moving that guy into the house with her I said it was okay or not was very manipulative controlling in that same friend said that she's being narcissistic because the guy she's talking to now after she breaks up with the one she was talking to is one of my friends and thought that was funny. She told me because she thinks I should know this time to go home but I don't know how.

How do you move on from someone you thought was your forever that you give your whole heart too provided everything possible. I just don't understand anyway thanks for any support advice or really anything hope everyone is having a great day