Men and women...what could be the case here?

Ok so normally I can't stand reading questions from insecure girls about their boyfriends not calling them back, blah blah blah...but this is really strange for my man. I left his place for work early this morning while he was still in bed (was his first day off in a couple weeks). He called me right after I got out of work but I missed the call because I was in a faculty meeting. I returned his call about an hour later when I got home, and he did not respond. I went about my business until about 7pm, and thought it strange he had not responded, as he is always very good about calling back promptly. I tried calling one more time and again, no answer. Then around 8pm he sent me a txt message (which he NEVER does and professes to hate doing), just saying "what are you doing." I responded that I was just at home relaxing and would love for him to come see me, and he hasn't replied. We have been together for over a year and this behavior just seems very standoffish and distant compared to how he usually treats me. I know we are both very worn out as we had kind of a long night out with friends last night...but should I be concerned here?