My sociopathic ex was dating another girl the last 2 mos of our 3yr relationship

I dated a guy for three years, he moved to my city after our first year of distance like it was nothing to leave the state across the country he’d lived in his whole life. We continued to date but now that he was closer he was very sketchy and often found himself caught in lies but was so good at talking himself out of them. I was so in love with him. We were off and on a lot but he was so charming and so good with his words I always came back. He had no plan, he worked at gas stations, landscaping, valet companies…but never kept a job for more than a couple of weeks. He was enrolled in classes but always skipped classes lying to his professors about deaths in his family or battling an illness. Whenever I came home from my job with exciting news or after a bad day, he always made it about him. He made me feel bad about being successful. He would lie about going to bars or getting high or selling drugs. He would always blame it on being depressed and then lie to me about going to therapy or support groups when he was really lacking out at the bars. I found him on dating apps throughout our relationship. Every time w broke up I said I’d stay away but he’d talk his way back in saying he’d prove himself. We broke up a few weeks ago. My friends had told me about a new girl he’d been seeing and I asked him about it (bc he was still sending me these messages about how much he cared) and he said she was just a friend and I was so much more. I told him if they were more than friends to tell me bc I didn’t want to come in between anything. He told me he loved me and knew we needed to break up bc he needed space to heal from his depression but once he was better he’d show me how great we’d be. I was out of town and when I got home I found a plant he’d given me that I couldn’t bear to have anymore so I dropped it off at his place without ringing the doorbell, just left it on his porch. About an hour later I had a message request on fb from a girl asking me if I’d just dropped this off at her boyfriends house and telling me she’s seen my name on his phone and I needed to stop. I screenshotted it and sent it to him with a question mark. He responded telling me she’s crazy and she’s not his girlfriend. I sent those messages back and this girl and I got to talking and I found out they’ve been living together (whenever we’d hang out it’d be on dates or a quick cup of coffee bc I was so busy) I showed her all the messages and it turns out they’ve been dating for two months, he told her he hadn’t talked to me since NOVEMBER. This happened yesterday. He was sleeping with both of us and dating both of us. I supported him through so much and now he’s working on “fixing things” with his new girl. I know I dodged a bullet but I’m so broken. I know all the lines he’s using on her and that was just me in that position showered with his love.