You were so dense. Seriously. How couldn't you notice his efforts? He was trying so hard not to be strict with you, so hard to make you see that he likes you. Yet you just didn't notice.
Going at him again, saying how he needed to lay off and chill out with being so strict and serious with everyone all the time, claiming 'It's okay to let it be sometimes', he just couldn't hold it in any longer. He had his own limits anyways.
It clearly made him worked up, since he suddenly spoke. "{{user}}, don't you realise that I'm not nearly as hard on you as i am on everyone else?!" He even slightly raised his voice. He didn't really say that he liked you, but you knew what he meant. He took off his glasses in annoyance and some mild embarassment, looking off to the side as he clenched his teeth.