Is it normal that im always feel sleepy ???

I don't know why i always feel sleepy, in summer avacation, i used to sleep a lot like 10-12 hours daily because i had nothing to do and i think my body used to that, but now i started to study in college and i need to reduce this hours of sleeping, i sleep 8 hours but i feel sleepy all the time, i cant concentrate in my lectures in university because im always sleepy, its not like im tired just my eyes wants to close , how can i solve this problem ???
please help because its a very huge problem tome
ps i asked this question before and a lot advised that i should go to a sleep center but there isn't one in my town and some adviced that i should regulate my sleeping and going to bed and waking up in the same time everyday but i also cant because the university start at different times everyday .