Marijuana Withdrawal?

I started smoking at age 12 and continued for 10 years. I've been off it for 3 weeks today. I started taking marijuana for anxiety without knowing it. I'm experiencing high anxiety, irritability, instability, anger, and boredom. I have an important interview tomorrow and I feel like I'm suffering in anticipation of it. It's hard to replace anything with marijuana considering I used it to produce interest in things. I flick myself off every time I look in the mirror. How can I take steps to cope with these feelings?