What can I do to deal with it and what's causing it? I never got it about school :(.
Could it possibly be because it's a new environment? Did you move away for college? Because homesickness could be the cause of feeling 'unwell' every other night. But to get it off your mind, maybe get a job, join some clubs/activities, or athletics, to where you think less about it because you're keeping busy all the time.
I didn't move away no. My parents live not too far away.
Also stay in touch with old friends and family. Helps with home sickness