Why isn't he responding to my texts?

I am planning on dating this guy and we made made plans already. I was talking to him yesterday morning and he was just fine. But then 5 minutes later, he stopped responding but I know he saw the messages. I sent about 4 more messages after, and I know he was busy, but still he'd usually be okay with me texting him. So no responses, but this morning, I texted him again saying good morning, he usually wakes up earlier than me and says it to me, but nothing and I saw that he saw it, I sent him 2 asking if he were okay and that he wanted to cancel the plans, no response. Why isn't he responding. He's acting weird and I asked if he had met someone else... Nothing either, I also asked simple questions, no response. Why is he reading all my messages but not responding cuz the last I checked, he said he'd always be there and that he knew that he wanted me... Which was yesterday... He also responds during work too...