When you add exercise, it's not uncommon to see a plateau or even an upward shift in weight as your body retains water. It's unlikely you're not eating enough if you're getting 1800 calories; going up would probably cause a gain.
Here's how SP calculates your calorie range: www.sparkpeople.com/resource/calorie_calcu
Writer, mother, wife, and breadwinner. I love to run, but running doesn't love me, so I'm switching to my low-impact bike.
I'm not pregnant, just fat: My blog. fatnotpregnant.blogspot.com/
| current weight: 186.4