Why doesn't he ever call or ask to hang out?

Well there is two ways you can handle this:

1) Back off, and by that I mean stop calling, texting, and asking him to hang out: either he will notice that and begin to pursue you or he will just let you go

His lack of calling you etc., could be more for many reasons: he might be seeing another girl or ex, he's insecure and doesn't like to initiate things because of fear of rejection(i'm this way!), he hasn't dated in a long time which makes him unsure how to handle things with you, or he is keeping you around and knows he doesn't have to put in the effort by calling you and such because he knws you will..

The second option:

2) Confront him casually on why he never calls you and stuff. Do not ask him about the relationship because if he is not calling you or asking you to hang out than I'm sure he is not seeing this as a relationship, so it might scare him off

I understand he is busy with school, but how busy could you possibly be not to send a text message these days. I had a guy I was dating who used to be "so busy with school", and I was in the same boat as you. I find out a few months later he was talking to his ex the whole time and enjoyed having us both in the picture at the same time. So before you jump into asking him about a relationship you need to figure out what is going on. My advice would be to do the second option first and casually bring up why he never calls you or asks you to hang out. If after that you see no difference, than go with the first option and back off. Some may say backing off is playing games but its not because there's only so far you can put yourself out there before you make yourself look like a desperate fool whos doing all the work.

*You asked if he would still hang out with you and not be interested...Yes he would. I know many guys like this, they have nothing else going on for them at the moment so they string the girl along, have someone to hang out with and hook up with, yet there not interested for an actaul relationship. See what happens after option 2 and 1..

firstly, whatever you do, DO NOT ask him about a relationship please! as things progress, things will lead to that on their own. it's only been a few months, keep it casual. act casual. act nonchalent.

you've done enough. dating is like chess. you've made enough moves. it's time for him to make a move too. don't initiate anything until he does. he obviously enjoys your company and as long as you're not a bug-a-boo, he will respond to your calls and texts. don't act clingy. don't over-analyse things. have a nonchalent attitude as well.

speak to him face to face about it but don't be accusive, just be like "hey, I've just realsied something... you've never rang me. why is that?" if he doesn't initiate anything after that then let it go and accept it. think about it, we are always told to "start as we mean to go on". so if this is what he is like now, then expect to always be the one to initiate and that can get tiresome! good luck!