Newborn and baby question: i am about to give up i am just so frustrated?

My son is 13 1/2 months and never really cared for solid food. Well now he rejects pretty much everything except the gerber lil crunchies,gerber yogurt melts,gerber fruit bites and occasionally some cheerios or something like that when I give him something new and if by god he likes it he will eat the mess out of it for the first 2 or 3 hours then won't touch it for a few months. So since he doesn't eat well he is on toddler formula but now is rejecting that he isn't loosing weight. He is a very active toddler running and playing he won't eat in the high chair. I just have no clue what to do I need some guidance I know his doc won't do anything since he isn't loosing any weight at a year old he was 23 pounds and 32 inches long