Is this the most confusing boy in the world or what?

Ok so in the beginning of the summer this boy who I've known for a long time asked me to hangout with him. We went to sit by the pool for like an hour and I talked to him one for day after that, but then he went to Europe. While he was gone his friend took his phone and texted me saying it was him so I talked to "him" all summer flirting. "He" stopped texting me and when school started the real guy ignored me. He's ignored me for the 3 months of school until 2 days ago. He messaged me saying he was sorry for being immature. I asked him if it was the real him and he said it was. So I forgave because it wasn't his fault the kid took his phone. We've been talking and I think he's flirting with me! What's going on in this kids mind? He acts like he likes me in the beginning of summer, ignores me, then flirts with me again? Do you think it's really him messaging me or "him" again? What should I do?