Going crazy???

Ok, so here's my brief synopsis of my life. I'm 26 years old. I work full time, and go to school full time. My grandfather, who was living with us, is now in a home & is dying quickly. Lately, I'm finding that I sleep an awful lot, and am continually tired and don't want to do anything. I already take antidepressants, so I don't think it's the depression. But, I literally feel like I don't have a grasp on life...I don't want to do anything. What do I do? Am I losing it mentally? People have told me to just snap out of it, but I don't know if it's as easy as that. Im usually a very disciplined & very driven person.....