iMessage messages don't come on time

Hei,

I have a problem with iMessage on my macbook. The problem is that the messages from people I talk to don't come in time. For example someone sends me a message and I don't see it, it doesn't pop out and after 10minutes or so I get the notification that I received the message but it says "10minutes ago". Why the messages won't come immediately? My internet works very well so I am assuming it's not it. Sometimes they do come on time and sometimes don't. I need help, it's really annoying.