Repetitive question but your response would be grateful!

I net between 1500-2200 cals a day (I manually set my diary to 1800 cals, so I just try to stay under my weekly goal)

at 1200 you need to eat your calories back, or maybe start at a higher cals per day. and then you have a better choice of whether or not you want to eat your calories.
I started at 1200 and lost some weight but then completely stopped even as hard as I was exercising. I wasn't even going to the bathroom enough because I wasn't eating enough. Lost motivation and starting all over again.

I'm now at 1500 and exercising every day, sometimes eating my calories back if I'm feeling hungry.

I have to agree with the other posters so far - when I go that low, I stop losing....

You are using the MFP calculator, so yes you should be eating back your exercise calories. You have days when you're netting 900 or even 600 calories. You won't hamper your weight loss efforts if you eat more and you will be healthier and feel better for it.

As for the stall in your weight loss, my bet is it's water weight. Weigh yourself less often and only at the same time of day. To give you an example of why, my weight fluctuates anywhere from 3 to 6 pounds during the course of a day, so it's easy to have actual fat loss get lost in the static.