he asked for my number then stopped texting me?

So this guy is in one of my classes at school, we're seniors in high school. We started kinda flirting and talking in class and then he started messaging me on a game called Ruzzle that we were playing. I stopped playing because it got boring and so that was pretty much the end of the conversations. So then he messaged me on facebook last weekend and we were talking and he asked for my number or whatever. We texted until he fell asleep. Then he texted me the next two days and we had great conversations, he asked about past relationships, was talking about prom, etc. Then he didnt text me the next day and I didn't really think much of it because we had only just started talking or whatever, but then the next morning he texted me about the homework for that class and apologized for not texting me because his great grandmother came into town. I was kinda surprised he was apologizing because I didn't really expect him to text me anyway. So i said how he didnt need to apologize and it was totally fine. But it changed things because then i kinda expected he was gonna text me but he hasnt. I texted him first wednesday and he stopped responding after like ten minutes, but i know he was out eating so he might just have been busy with his family. Then he didnt text me yesterday either. Today in class he acted normal and was talking to me and stuff and it wasn't weird or anything. He came over to my desk and I said "can i help you" and he was like fine see ya or something so i felt really bad about that but we talked during the rest of class so I don't think it was a big deal. Whats going on here? Why would he start texting me and then stop? I mean it kinda took effort for him to randomly message me on facebook and then get my number. I texted him to apologize for class today and he said it was fine but stopped answering after a few texts. any advice would be great thanks