Possibly he's getting a neg vibe from you. I know its so difficult not to show how we feel.
Read over your posts from last week. You were getting affection from him. Or read over posts from even 8 months ago and see how far you guys have come.
Or maybe he was just thinking about other things this morning. I said ilu this morning before my H left and he didn't say it back. At first I was a little worried - but then I remembered he told me about a case he was worried about last night - and what he needed to do today.
Life certainly gets in the way of our efforts sometimes... But thats something that will never go away.