Why is my friend doing this?

so I'll try not to make this too long....but I have a friend who started to talk to me on Facebook about 5 months ago, and a week after he started talking to me he told me that his friend liked me....and then he told me that that wasn't the reason he talked to me. well we became really close (as friends) and he made it clear that the only girl that he liked was another girl who lives several hours away from him. we started to go do alot of things together, then recently my sister came home from college (he's 16, I'm 14 and my sister is 20....and she has a boyfriend) and then he started to talk less to me less on facebook, and then I hung out with my sis tonight and he started to talk to her, and then he asked my sister if she and i and her bf wanted to go to a movie with him and another friend....(he didn't know that I was sitting in the room when they were talking) and then I got on fb while they were talking, and it said that he wasn't on...so obviously he blocked me from being able to see him on there......ahhh what's going on? I don't like him or anything, I just want everything to stay as it was!! thanks to anyone who answers :)