Why didnt he answer my message?

so this guy added me on facebook and we were talking on their for a long time. It seems like hes interested me and he wants to hangout with me and stuff. he even gave me a cute nickname and everything. then we stopped talking for weeks and then he started to poke me on facebook and then he sent me a message saying "heeeeyy" i answered and then we had a long fun, interesting conversation again but he didnt reply to my last message! he did go online though because he updated his status twice, so is he ignoring me? or is he just not interested?? he has a gf by the way but it seems like he doesnt like her.