Exercise calories

Hello everyone....looking for a little guidance. Been counting my calories for just about 13weeks now, eating 1200 per day, and have lots 21pounds. The last 3weeks I have been going to the gym for least 30 to 45 minutes of cardio x5, but I'm not eating more then 1200 a day still. The scale keeps going back up a pound or two then back down again. Can't seem to get into the 20+ loss. Wondering if I'm slowing down my weight loss because I'm not eating enough now. I'm too scared to eat more and not lose or gain weight back??? Any trainers or knowledge people out there can help me out with info???