Question from Parent of Toddler: Eating Problem

Help Help! I have a healthy 15-month old son who is still eating jar baby food. He has sat in his high chair with us at all meals since he was 4 months old. At every meal, we offer him bite-sized pieces of our food, but he just mashes it with his fingers and will not put it in his mouth. If we put anything in his mouth, he gags on it and spits it right out. He will self-feed Gerber cereal squares and Gerber crackers and Gerber fruit and vegetable puffs, so he does not seem to have any problem chewing (he has six teeth) or swallowing solids. My pediatrician says not to worry about it, he will eat when he is ready, but many of my friends say I should tough love him by not giving him any more jars of baby food. Any advise for this frazzled first-time mom? Thanks!
Kerri