That's just how he is
Everyone's different, that's what makes life so exciting. But it can also be what makes life so confusing.
When you first start a relationship you suddenly become very close with someone who you probably don't know very well at all.
Maybe you're a real communicator and love to text back and forth all day, whereas he's more of a face to face person who likes to wait until he's with you in person to have a chat.
You might be offended by the fact that he takes two hours to reply to a message or that he rarely texts you during the day. In fact, you might even get yourself in a right stew about it, while he goes about his days totally unaware that there's a problem.
Once again, talking to him is key!