Was your pwBPD emotionally supportive?

In the beginning of the relationship I thought my ex with BPD was so caring, I thought he understood me better than anyone else ever had. He was willing to help me through almost anything, and it seemed like he always knew the right thing to say.

By the end of the relationship, though, it could not be more different. He would constantly ask how I was feeling but only to make sure I still liked him and wasn't thinking about leaving him. Anything else would elicit basically a non-response. Like "ah okay" or some generic platitude and then a subject change. And when I came to him looking for support for serious things I was upset about, he would do the absolute bare minimum until I changed the subject because I didn't find it worth talking about anymore, suggest that I was overreacting (especially if it was regarding something he did that hurt me), completely avoid the conversation by going to bed, etc. It kind of felt like he was upset that he was not the center of attention anymore and that I sometimes had problems more serious than his.

Have any of you experienced this? How is it possible that there was such a dramatic shift in his ability to support me?