For what it's worth, it's kinda funny this thread was upped right now, because after three years of no contact I recently talked to her. Basically, she apologized and told me, that what caused her to "run away" were severe anxiety issues. There isn't really much I could have done to prevent this, because this is a pattern for her. Sooner or later, her mind goes into overdrive with negative thoughts, causing her to panic and leave. That's also why she had told me not to chase, because that increases the anxiety, while she had hoped that it would die down after some time of separation. In retrospect, I think that there were some things i messed up, but the main problem was that she didn't tell me about her anxiety (part of her anxiety is panicking about her anxiety and fearing that people will think she is crazy) so that i could have taken it into account and help her deal with it.Even though this happened to you three years ago I want to share my story so that maybe it'll help someone going through a situation similar to yours.
I was in a relationship with this guy about a year ago for a total of three months, only I was the dumper not the dumpee. Soon after we were together I began to realize that I was putting in way more than I was getting out and I brought it up to him twice. I don’t think my concerns were unreasonable and he completely agreed. I was having similar concerns as your ex, like him not making any efforts of contact/plans for major days for me, when we did go out it was always something he wanted to do or even basic day-to-day contact revolved around his schedule and always conflicted with mine. It hurt that I was never really considered and I began to feel a bit lonely. He always reassured me that he would do better but he never did. I would have called it off sooner but he always talked about us getting married and having kids and his excitement for the future made me excited. That added to the frustration because his actions did not line up with what he was telling me so I eventually had to cut ties. I reached out twice within a two week span after we broke up to see how he was doing and if he was ok but he never responded. Honestly cutting off contact completely was strange and difficult but I just wanted to hear his voice maybe one last time. Sure, me reaching out wasn’t fair in terms of his emotions but I didn’t want to rehash anything but how could he have known my intentions. In retrospect, it was for the best that he didn’t respond.
I think if you’re in a relationship and someone brings up concerns similar to the ones I had and the OP’s ex I think you should ask yourself if you’re really into the person you’re in a relationship with. Maybe you can be the person to call things off before you’re slapped with a breakup that you deem unexpected but might have been brewing for the other person for awhile.

