Your GP is a good place to start. They can discuss your problems with you and get you into treatment.
They may offer you treatment at the practice or refer you to your local drug service.
If you're not comfortable talking to your GP, you can approach your local drug treatment service yourself.
The Frank website will give you details of local drug treatment services.
0300 123 6600
The Derbyshire Substance Misuse service is based in Ilkeston and will also be able to provide advice and support.