Great Disappointment

I agree with the suggestion of getting your thyroid checked. Also, if you're ever dipping below 1200 calories, it doesn't matter how hard you're working, it might be turning your body into starvation mode, which means every calorie is happily clinging to you. I'd also recommend that while you're at the doctor asking about thyroid, ask about everything else you can think of - if you have a family history of diabetes, get some glucose testing done, etc. And, check your Vitamin D and B12 levels. It's not likely you're deficient in both (though I am woohoo), but if you are deficient in one, it might be helping the yo-yoing. Lots of people are not getting enough Vitamin D and I've seen a few recent studies suggesting that if you're low on Vitamin D, you might be overweight and that the vitamin might help you lose some weight. Vitamin D can't exactly hurt you so getting a few extra minutes of sun (with sunscreen) or adding a daily vitamin to your day couldn't hurt and might just help you break through this range you're stuck at. At any rate, don't give up. Every time I hit a wall and start to bounce back up, I get really upset and often won't admit to myself that I give up for a while. Then I always regret the time I wasted feeling frustrated. Better to be frustrated, head to the doctor, and keep working at it than to work at it, be frustrated, have some amount of progress, and then stop working at it. Then it just means doing it all over again in future. Good luck!