I stole money from work a few weeks ago and spent it on heroin and meth

I am a 21 year old addict. I stole about $1600 from work over the course of 2 weeks. I used it to buy heroin and meth. I need to pay it back before they notice but I also really want to get high. I don't know what I should do. I don't have a car so I can't sell my car to pay them back. I don't have anything valuable to sell. I am so anxious I can't eat or sleep. I am in school and I have no idea how I am going to focus now. I just want to get high and forget everything.