I'm sorry you are going through a hard time like this. First, let me say that I'm really glad you are working on your mental health. Seeing a therapist, taking your medicine and working on you is the right course of action. No person such as a boyfriend or place such as a new start in Denver will ultimately make you happy or less depressed for real. The band aid eventually falls off. Facing the situation of our mental state and what is going on inside of us is brave and essential to actually recovering from it. :>) So, you are on your way.
I would imagine he was genuine, your ex. But you had placed so much over the top emotion on him and needing him that he felt smothered by it. Adults need to be interdependent in their romantic relationship, not dependent. That means you are two separate people, standing on your own two feet who are enhanced by the other. You aren't dependent on that person for your joy and happiness. They bring these things to you but you don't need it. You were in a bad place when he was in Dallas and were just 'too much'. He's trying to get his career going. He wants to bond with colleagues. And you kind of made it all about you. I hate to say that and am not judging you but just speculating for how he might have felt and why he broke it off. He wasn't ready to be your everything. Too much pressure and stifling of him.
In your next relationship, you will be stronger. You will be healthy mentally. You will be able to have a life WITH your partner but also away from him and can accept that he does too. Does that make sense?
It's unfortunate that he thwarted your plans to go to Denver. But it doesn't sound like he was doing it spitefully. It sounds like he does care for you, would love for this to work out but that you were in a bad state of mind, which scared him. ??
Keep working on you, stay busy, and we are here to chat any time!