I'm devastated and don't know what to do

Last year, my boyfriend of two years started talking to his baby mama about more than his kids. I confronted him. He denied it all. He said he was over her and they both moved on. Now after a year I went through his phone. They've been flirting for a few months.. She said she missed him and he said it back. She asked about me and he said that we don't compare to what they had. How could he say that to her ? After everything we've been through and what he's told me. I told him it was her or me and he broke up with me. He Said he couldn't do this anymore & then switched it and told me I fucked up by going through his phone. . I don't even know how to feel right now. I don't deal with heartbreak good so I done even know how to get over him. I feel devestated. I risked everything to be with him and this is what he does. I only wanted to be with him. I keep thinking of him and my heart feels like a huge hole is in it. I just keep crying and need encouragement. Why would he just leave me ? we've had our differences but it was nothing we couldn't work through. How can I get over this ?? I feel so helpless.