Need Encouragement
 

I have been dieting since Jan. 3rd of this year. I am not sure what I weighed then...I was too scared to get on a scale. I joined the gym on Jan 21st. I have been going to the gym 4-5 days a week. I recently joined a 90 day fitness challenge at my gym. I went into today to do my initial weigh in and I have lost 13 pounds since I joined on Jan 21st. I was feeling really good about my weight loss for a few minutes. The weigh-in also included my body fat %. The fitness trainer said that "you have got a great jump start on your weight loss but you have loss have the pounds in muscles and that is not good". So, I am assuming that I have been doing way too much cardio and not enough strength weight training. Anyone with this experience know how long it will take me to build those muscles back? And will I put back on those pounds?