D.W.
I'd say this is more common than not. Our kids did the same thing as they became more adventurous and had better chewing abilities, etc.
The best thing you can do is offer healthy foods and not cave in when he won't eat. Children do not go hungry. But, they will manipulate us until they get what they want.
Out of curiosity, is there a particular reason you still have him on formula? With both of our kids, the pediatrician said to skip the next step formulas and go straight to Vitamin D milk. Just wondering based upon our experience.