I got pregnant at the age of 16 and ever since I had my daughter it seems impossible to gain weight Im 18 years old now and I cant even get to 100 lbs What can i do?

If you are trying to gain weight by eating a lot of junk food, DONT DO THAT! You will just become very unhealthy. Try eating all food groups during breakfast, lunch and dinner. Also try to exercise and build muscle instead of fat.