Ugh, I've been struggling

I am trying hard not to let one day derail me but man is it ever trying to do just that. I cheated on Saturday and then ate more than I should have on Sunday because we had so many left overs and then yesterday I tried hard to be good but it is like some hunger switch got flipped inside me and I was starving all day and ended up eating about 350 more calories than I should. I got on the scale today (even though I said I wouldn't) and I am way up, it said 255lbs. This was after I ate both breakfast and lunch and had quite a bit of liquid to drink as well, so of course it was up. What am I stupid???
See the thing is, I woke up on Sunday feeling like crap. Not just mentally but physically. Ever since then I have been tired, sluggish and just felt like crap. I didn't feel like this for one second in the last few weeks while I was dieting. I had a spring in my step, now I feel like I'm struggling just to step at all. WTF? You would think that this alone would be motivation enough to pull me right back. Maybe getting on that scale every day is more of a motivator, even if it doesn't move for a few days in a row. I have been trying real hard to get back on track. This is where I usually fail. I want this time to be different!!