Why can't I stay awake in cl?

I'm in college and my cles usually begin in the afternoon, so I don't go to sleep until 1-3 AM and I get 7-9 hours of sleep every night. I wake up, shower, and then eat a meal (usually a wrap with ham, cheese, and lettuce) and gs, and then I get my bag packed and head off to cl and I doze off in almost every cl for some reason. Does playing video games or watching TV before bed or eating a milkshake at like 11 PM every few nights have anything to do with this? I can't figure out what I'm doing wrong because in high school, I would be tired the first cl or two, but by the time I got lunch in me I was always wide awake and attentive. In college, I just can't stay awake for some reason.