Just to let you know, my 15 month old suddenly started to not eat either. He's not gagging tho'. But he will sign very eagerly he's hungry, go crying to his high chair to get up. So I set him down, prepare his favorite food, only to have him take one bite and then say he's all done too! It's really weird because I know he's hungry. He's highly irritable, cranky and always asking for food. I took a look in his mouth yesterday & sure enough he's cutting all 4 of his eye teeth.
Luckily for me I didn't have him totally weaned so we are back to nursing more than I wanted to be, but it seems to be satisfying him some. So far he's up to eating apple sauce and most soft cereals like oatmeal. Maybe try something new and soften the harder foods, and maybe he'll regain interest. If not maybe some pediasure just to make sure he's got the essentials for the most part.
As for something being stuck I think he'd be showing a little be more signs outside of eating, but anything is possible. I would say if there isn't some kind of improvement in the next week go ahead and bring him back, and have him looked at again!
Good luck, hopefully its just a phase right :)