Am I losing my best friend?

[Daniel]

I've known him since we were babies,we did everything together as kids,we spent the night at each others houses every Friday,my mom babysitted him,and we went to each others houses after school everyday. But he had to move,and I didn't see him for 3 or 4 years,until I saw him on Facebook,so I added him,and we started hanging out for a few months,but then he just stops talking to me,I haven't talked to him in atleast 4 months,I try to talk to him on Facebook,but he just looks at it,and doesn't reply,the first few weeks I tried to see if he could spend the night,but he said he was busy everytime i asked,then after that he just started ignoring