Yes, I know what you're talking aobut. I went clean about 3 months ago, and it's still hard at times with cravings. Not so much for processed foods, but for sweets! What helps me - and this is kind of weird, but it works - is having a glass of water with greens (I use Vitamineral Greens). It's a powder you mix into water and it has all kinds of healthy greens in it. It's raw and vegan.
Also, I came up with a "compromise" for myself as far as sweets go: I got rid of everything in the house except some dark chocolate covered almonds that I treat myself to when I really have a sweet tooth. I figure it's not all that bad.
In your case, you could just try to phase out the bad processed foods slowly, instead of all of a sudden. That might help...So instead of eating clean 3 days and then eating bad one day, you could just eat 50% clean for a week, then 75% clean for the next week, and so on. That might make it easier and help with the "relapses".
Best of luck! Hang in there, it's so worth it.
Eva