He likes me but never calls

this guy I've been dating recently asked me to be his girlfriend - but he admitted he'll forget to text or call at times and for me not to take it personally. I really like him and I'm trying to take it very slow because this is a new relationship and I'm trying to assess how he feels about his space.he'll call me to hang out and stuff but never to talk, and now I'm on a week holiday and have no idea how I should approach this, since I'll text him he won't text back or text back hours later, but deep down I do know he likes me. can guys just explain why some guys don't call or text back sporadically. it's really odd, esp when they say they like you. btw he hasn't had a girlfriend in about 2 years and is apparently super picky so I know him asking me to be his girlfriend means something.but still, any ideas how to approach this or ask him for more without sounding nagging or seeming desperate? and also what does it mean when a guy does that?