I find myself blowing up his phone asking for him to talk to me, answer
my texts, but then when he does I just go into that “I don’t care about
you anymore” mindset. Why is that? Am I trying to convince myself I
don’t care?

I think why it is that you go into that "I don't care about you anymore" mindset could be something to do with family or drama, but I wouldn't say for certain. It could also be that you need a new outside perspective and/or to look at things from a/the bigger picture about where you are both headed. I think you are just trying to think of new things and ways to look at things, not that you are trying to convince yourself you don't care, and you just don't know how to go into thinking about that just yet, until this, hopefully, and you just need a new perspective and something new. That's what my guess is, but I can't say for sure.

Can anyone please tell me what is wrong with me? Why do I think/feel this way?

I'm not sure anything is "wrong" with you, per say, but I do think you could do better with some help because we all can do better with some help. Why I think you feel/think this way could be something to do with being in like a brain cloud of thought where you just need to see some light from someone else and let it into your life to renew. I hope this helps.