Long distance relationship advice

Hey guys I've been having mixed emotions about this. I really need an advice and I would really appreciate it if you give me an advice. This is kinda lengthy so bear with me.

Okay so I'm with this guy and we've been together for 2 weeks already. We have a 12 hour time gap so it's been really hard for us. He lives in Canada and I live somewhere in Asia. It's his first time in a long distance relationship and it's my second time so I'm kind of used to it. After two weeks, he broke up with me saying that he didn't realise that he's too busy to give me his time and that he said he lived in a fantasy those two weeks we've been together. So the break up lasted a week and I've been really heartbroken ever since. On the 8th day, he messaged me saying he wants me back and literally begged me to get back with him cos he said he realised that his life isn't complete without me and that he misses me so much and loves me so much that he promised he will never leave me again.

I was too hurt that I promised myself I won't subject myself to that kind of pain ever again but he asked me for another chance. At first I really didn't want to give him a second chance but I decided that I should. We both really love each other and I can really feel this burning chemistry between us but the thing I want to ask advice is about effort.

You see, I'm studying medicine and I'm pretty busy but I still give him my time and text him so often because communication is crucial in long distance relationships right? He's already enrolled in Law but right now it's summer time so he shouldn't be too busy right? Whenever I message him, it only shows delivered and it would only show 'read' most of the time after 6 hours or 8 hours when it's his bedtime which is 2 or 3 am.

It's just really frustrating because it's summer and I know he's enjoying his time with his friends but seriously he only messages me when it's his bedtime or sometimes when he wakes up. Keyword is sometimes.

When we talk, it usually lasts for just 2 hours maximum. I always message him and wonder why he's still up by 2am, doing who knows what with his friends. He said he's a very social person and is an extrovert. I always try to understand that but if I can give him my time even when I'm busy, why can't he?

I tried confronting him once and he just gets upset saying that I can't message you 24/7 and I try to understand that cos he has a life other than me but it's just.. its hard to explain to him :(

I feel lonely sometimes because I feel like I'm on the least of his priorities. I asked him about it and he said that I don't have a number cos I'm the whole list but I don't know I just feel like there's a lack of effort on his side. :(

I really don't know what to do. Help I need girl advice! Thank you so much for those who would give their opinions. :*