Exercise calories

When i first started using MFP I was a little confused about earning calories back after you did a work out. I figured working out was to burn calories and eating them back seemed pointless. I work out every day, whether it be P90X or just going on a run, I'm always burning some sort of calories. (I also babysit two toddlers so I'm running around crazy all the time) MFP has me eating 1200 calories a day but I have been reading that eating under 1200 calories a day could actually hurt me in the long run, so I'm confused on what to do with my exercise calories. I am under my calorie goal every day because I have not been eating them back. I am currently losing a healthy amount of weight (1.5 lbs a week) a week but I don't want this to stop! Does anyone have any advise? eat back the calories or just stick to 1200 and not worry about it? Thanks for your help!