if your losing weight then you are not eating enough or getting inadequate calories from the foods you are eating.

if your not getting enough calories to support the exercise you do during the day then you will drop the weight as the body find a source (bodyfat/muscle) to get it from.

high protein diets will stop the catabolic (muscle eating) process from destroying your hard earned gains in the gym to a degree but you need to have the carbs in the diet too to stop you losing weight. Are you looking to gain weight or maintain the weight your currently at?