Anger and numbness

I am 23 years old. My life has been terrible for a long time, but it's worsened progressively over the past year and a half, and I've been feeling depressed for a long time.
But, lately I got some really bad news, which was like the last straw for me. Since then the only emotion I seem to be able to feel is intense anger. When I'm not angry I just feel completely NUMB. I have lost interest in everything I used to get pleasure from. I don't feel like doing anything at all, except sleeping as I feel EXHAUSTED all the time. Even though as a rule I have never been one to sleep more than 4 hours a night.
I have always had a pretty bad temper, but lately it seems much, much worse. I get really angry at the slightest thing and have moments where I feel like I am going to snap completely. Then, about half an hour later I feel devoid of emotion again. What is wrong with me??? I'm starting to get really scared D: