Idk why I'm so sad about this!

My bf & I have been together for 3 years now. I only see him Thursday's-Sunday's because we go to different colleges. We always text each other throughout the day & make sure we at least call each other at night, even if it's just a short call saying goodnight. Today he got home from school around 9. He texted me at 9:30 & around 10:15 I called him. He said he was still studying & needed to finish. Recently I've been trying not to annoy him, so I waited 2 hours for him to text or call back when he was done. I was so sleepy so I called him. He answered & said he accidentally fell asleep studying & said goodnight & went to bed. I stayed up 2 hours for him so I just wish I would've known, I just don't know why I'm so butt hurt over this.