My boyfriend is too busy for me

So my boyfriend of almost 3 years recently moved away for college. We are both 23 but I went straight to college and he started working after hs. I was proud of him for making the decision to go to school but sad that it had to be so far away. I stayed with him over the summer cause I had just graduated and did have a serious job. Now I'm back home. He is working and going to school so he barely has anytime to talk. Literally all he does is sleep,school, and work. I ask for him to call me before he goes to sleep no matter what time but he keeps falling asleep before calling me. I recently told him I feel like we've been fighting a lot and times are more unhappy than happy. He was upset by me saying that cause he doesn't agree. He said he knows he hasn't been able to give me a lot of attention but it's cause he literally has no free time. What should I do? I want things to be different but he's independent and needs to be working and going to school to better himself.