I've developed an unhealthy mindset while dieting?

I agree that you should probably speak to someone. Hopefully this is just a rough patch you are going through but it's a good idea to start changing those thought patterns to something healthier before it becomes a serious problem.

In the mean time, here's a blog with a great common sense approach (in my non-expert opinion) http://dropitandeat.blogspot.co.uk/
She deals with all types of eating disorders so some posts may not seem relevant to you but it is worth reading because she talks a lot about 'normal' eating - learning your body's signals, eating food that satisfies you, making mentally healthy choices.

Even if you don't go and see a counselor now, please tell your parents, your big sister, your best friend, SOMEONE what's going through your head. The problem with eating disorders and most mental illness is that when you relatively well, you don't seek help because you think you can manage it. Then when you get sicker, the illness prevents you getting help because you are too sick to realize you need help and reach out for it. You need other people watching out for danger signs.