I am a teen mother who is currently breastfeeding my five month old son. I cannot lose my pregnancy weight what can I do? I eat healthy and exercise.

Cardio Mix. If you have adipose tissue that you'd like to lose then consider an increase in cardio and a balanced diet. However, do not always do the same exercise or you will increase your risks for stress injuries. Mix things up with running, biking, swimming, or circuit training. Ultimately you need to burn more than you consume.
Discuss with PCP. Work with your pcp or nutritionist to decide on a proper food intake that would support your pre-pregnancy weight. Then just stay on that program and continue to breastfeed. You can drop 1-3 pounds a month with this method ; it should stay off.
You will lose weight. If you are eating a healthy well-balanced diet and are exercising you should lose weight. If you are not accomplishing this you should see your physician so that an evaluation can be performed.