Hey,
I have the exact same problem hun. I know what I'm doing is wrong...and I know it's an addiction, but I find myself plotting out how to get my hands on my next block of chocolate/bag of lollies/ice-cream/biscuits etc.

I went to the Naturopath a few months back, and she gave me a rude shock about what I was doing to my body. She also explained why I was stuck in such a nasty cycle. Basically, she laid out an eating plan for me (plenty of vegies, fruit, protein and some grains) and just told me to do it. I had about 3 days of feeling more rotten than I have in a long long time (caffeine and sugar withdrawals) BUT after day 3 I started to feel better. Then I hit a patch of time where there was always a morning tea at work, and I was working late, so just grabbing whatever I could, and I got back in to my old ways...and I feel so much more revolting eating this way again that I'm going to start looking after myself from today.

It sucks - I feel run down because I eat rubbish, but then because I feel run down, I reach for comfort food (which is more rubbish) so I keep feeling run down.

Good luck hun. xoxo