Weight loss stop

Are you weight training? If you are experiencing significant muscle soreness you body is retaining fluid to help repair the muscle fibres.

You would do well to be at least eating to the calories allocated, significant undereating is usually counter productive in the long term. Make sure you are at least meeting protein and good fat targets.

Weight loss sometimes temporarily plateaus when you start exercising. It's because you might be losing some fat, but you're probably building some muscle, so it balances out.

Second the suggestion to be drinking enough water. Also, make sure you are getting enough sleep and taking rest days (or lightly active days).

Also seconding eating enough. Your allowance is your allowance for a good reason, and so you shouldn't really be eating "far below" it. (That said, you don't have to eat back any of your exercise calories if you don't want to. So I mean your pre-exercise allowance.)*

*Exception: If your exercise drops you below the minimum recommended "healthy" # of cals to have in a day (like for someone like me it is 1200 min) then it's a good idea to eat at least back up to that.

When my son joined the Army, after Basic Training he gained 20 pounds and was in great shape. Of course he was a bit underweight to start out with. Unfortunately, now he's sedentary and overweight.

If you only started here two months ago, how long ago did you start at the gym and stop losing pounds? If it hasn't been longer than a week or two, press on. A new exercise regimen can cause temporary water gain that could be masking your fat loss.

Are you entering your exercise into MFP and then eating those extra calories? If yes, where are you getting the calorie numbers? If it's from MFP, those numbers are often overinflated and could be cutting into your calorie deficit.