Do You Think His Ignoring Me Or Just Not Online?

i really like this guy on facebook and i messaged him and he messaged me back saying how nice i was. so i messaged him again 3 days ago saying we should meet up forsure (his idea) and told him afew other things. Anyway he hasnt gotten back to me in 3 days! i know i sound clingy but i have OCD and such. anyways he hasnt posted anything new since 3 days ago or more. so do you think his ignoring me or just not online??? he does go to collage/uni maybe his to busy. should i be worried?