Sounds like depression of some kind — does your school have any kind of counseling program? Your employer likely has an EAP, employee assistance program. EDIT

Sounds like depression of some kind — does your school have any kind of counseling program? Your employer likely has an EAP, employee assistance program. EDIT 1: Plus-one for the commenters suggesting doing something with other people — especially something that benefits kids, or others, who are less fortunate than you (it's an amazing mood enhancer). EDIT 2: Absolutely be sure to get regular, vigorous exercise of some kind — even just rapid walking — to release endorphins.