Very picky eater...

My son has been picky from the moment we started solids at 5.5 months. He would gag on basically all of the baby foods except bananas and sweet potatoes. Eventually he added a couple more that he would tolerate and Gerber puffs. Fast forward to present day (15 months old). He will eat a variety of Step 1 baby food. If it has anything but smooth texture, he still gags. Mashed banana is the only one that he deals with the texture. He eats crackers and Belvita breakfast biscuits so it's not like he can't handle foods with a crunch. Cooked pasta makes him gag and make faces just by touching it. We keep trying different things different ways. He has been completely off breast milk for a week now (he was getting a couple 4oz bottles daily). I try not to give him too much whole milk so he won't get full off of that. He probably drinks a little too much water, but other than that, I just don't know. His 15-month checkup is soon. I'm just wondering if anyone else is having troubles with eating? He won't even do cubed sweet potatoes. Sorry this is so long...