Hey man, I was EXACTLY in your shoes. Like I mean literally I could have written this myself and I probably did at some point. My ex did the same exact thing. It’s a rebound. They can’t face the emotions on their own so they use someone else to get over it. It’s horrible. I even asked my ex after she broke up with that guy why she did it and lied to me, and she barely could answer me because she knew she didn’t have a good reason. Trust me, it won’t last with them, she’s just using him. All she’s doing and all my ex did was SELFISHLY get with someone else to try to move on easier, it’s a shitty thing to do and they wouldn’t have liked it if the roles were reversed but since they’re selfish they don’t put themselves in our shoes, they just care about how they feel. You don’t deserve someone like that, someone who lies to you and treats you like that. I know it’s hard to hear cus I’m in your shoes too, but we need to find someone better and we will. They’re out there. Anyone is better than someone who does that to someone they “love”. Good luck man