When a guy stops showing sexual attention?

my crush used to show a lot of sexual attraction to me (blatantly ogling me, brushing against me, innuendos, using "love" as a verb rather than a noun, jokes, sexual topics) and I would reciprocate. We were just class friends and never hung out. But then one day at school he showed dominance/manliness by towering over me, showing off his abs and grinning evilly when he caught me looking. I looked away, bashful (usually im not). since then he never mentions anything sexual to me, no longer looks at me lustfully (unless I do first) and changes the subject if I do make an innuendo. instead he just offers continuously to help me with homework, is concerned about not showing respect, and tries to get to know me. He gets sad and insecure if I dont show him regular attention, and is anxious and unsure around me. I also noticed there is no longer sexual energy emanating from him, just a feeling of sadness and longing.