Boyfriend ignoring me after long distance visit?

My boyfriend and I met in middle school and reconnected as friends on Facebook two months ago. He lives on the east coast while I live on the west. We talked everyday and decided to date before seeing each other in person after 10 years. Two weeks ago he flew out to see me and stay with me in my apartment. He seemed happy to be here the first day, but after that he rarely smiled, talked to me, initiated a conversation, made eye contact, and just seemed like he was preoccupied with his phone the whole time.

Now that he's back home, he hasn't been very responsive to my texts and won't pick up his phone. I'm supposed to fly out on Saturday to see him (I paid for the ticket) and I can't get ahold of him. What should I do?