Confused! mixed signals?

okay so there is a guy i know, hes a close family friend of mine and hes a 4 years older than me, im 15 and he turned 18 the other day. since last year he has been starting to show interest in me, like his mum tells me he thinks im beautiful but cause im younger he's afraid to tell me things like that. The other day he had a party and he got really drunk and came and sat next to be me in the front room where he placed his hand on my leg and left it there, i got so flustered that i pretended i needed a toilet but i came back and he did it again. Later on he came and put his arm around me where he pulled me into him and i was literally leaning on him and he whispered to me that i was a 'really good looking girl, and i could get any guy i like' he said i was really pretty, he then bet me that i could get anyone i wanted and looked into my eyes for about 10 seconds after he said this, then later he came and sat with me put his arm around me and kissed me on the forehead, next when we went into the other room i was with all his friends and just as we were about to enter the back room he pulled me back told be how beautiful i was and kissed me on the forehead again. However as our families are really good friends we went over there the other day where i found out that he had got back togethere with his ex, and he didnt speak to me once and ignored i was there really. So i just want to know like what the hell is his problem, can you help?