I know I don't have all the details, but..
.. Sleep 8 hours a night
Rest from exercise for a couple of days
Then increase your exercise intensity
And go back to 1800
.. if you're getting as much sleep as before and the only thing you've changed is your food then maybe you could increase your exercise intensity and keep your food at 1800. That way you get the calories, but still get a deficit.
Do you feel you are ready to change your exercise from low intensity to some high intensity workouts? That may be something to look into.
If so, you can burn 500 calories in 26 minutes doing Tabatas according to "Muscle and Fitness, Hers" magazine. But they are very high intensity so you'll need to be ready. You could start with interval training instead. Then, if you do some weight training for 15 minutes on top of that, you'll not only gain muscle and increase your metabolism, you'll also burn calories throughout the day (after you've stopped exercising).
Then you can continue eating the 1800 calories and still drop weight.
Also, you could be burnt out or sleep deprived and just need to rest for a couple of days, take two days off of exercise and get some sleep in to catch up. I had to do that recently and feel so much better. I have a baby and didn't realize how much I was taking on or how sleep deprived I was. Emotions went down the hill as well. Once I got strict with my sleeping schedule (7/8hrs minimum a night for me) and rearranged exercise around that, I felt much better.
"How does one become a butterfly? she asked pensively. You must want to fly so much that you are willing to give up being a caterpillar." - unknown
Start Weight: 235 lbs - Sept 2010 (9 months pregnant)
Focused weight loss efforts began: 212 lbs - Dec 2010 (as documented in Fatsecret)
Goal: 130 lbs Summer 2011