Dennis wasn't upset with her so much as just upset in general. He was stupid to admit his feelings to her. He should have known but what hurt the most is that she pitied him so much she'd offered to kiss him even though she wasn't interested. That stung quite a bit.
He sat up as well, "I'm not upset," he said quietly. He didn't feel much like cuddling anymore though. Crying, maybe... and god he was pathetic and pitiable.