Help! [+REP]

My sleep pattern changed for these few days. I used to sleep at 10pm and wake up at 6am or 7am(That was when my schooldays). Now, I sleep at 10pm and wake up at 11am-12am(school holiday). I find this very unhealthy and when I woke up, I feel sleepy and feverish. I haven't had a period for 1 month+ and I've always had my period later than the previous period date. So, is it because of my period and that I'm actually having a cold or because of other reasons? This is the first time it's happening. I didn't have problems like this even though my period is always late. How can I change my sleep pattern back to my normal schooldays sleep pattern? Please help as I'm going to work soon and this problem will definitely give me a lot of trouble. :):):):):):):) +rep for all posts