16 month old still won’t eat anything

Does anyone have experience with a toddler that refuses to swallow solid food? Some background info:

I started my son on purées when he was almost 6 months old. He took to them very well and seemed to really love them. I spoon fed him and he would use a self feeder spoon as well. Around 8 months, he stopped taking them completely. Refused us spoon feeding him and he wouldn’t touch it. We tried other safe foods around this time with different textures and he refused everything.

Around 10 months, he finally started picking up solids (mostly the gerber baby snacks like the puffs and crunchies). He would put them in his mouth, but he would spit them out instead of swallowing. And this is how it’s been for the past 6 months. He goes through phases every so often where he refuses to even put anything in his mouth. There have also been times when he will swallow a few things, but only a couple pieces per day. Any time he is given fruit or veggies, he either refuses them completely or will put it up to his mouth but not try it.

We are currently seeing a speech language pathologist for feeding therapy, but she doesn’t think there is a swallowing problem. She just thinks he’s stubborn. She is encouraging us to keep trying and keep it positive with no pressure on him, but I don’t feel that we are seeing much progress. We haven’t been working with her for very long (only about a month I think), but I was really hoping for better advice than “keep trying” like I have been told for 6 months.

To further complicate things, he is allergic to dairy, eggs, and peanuts, so I am very limited in what I can offer him. He doesn’t often show interest in what I’m eating, but when he does, it is almost always something he cannot have.

He is still completely on hypoallergenic formula, which is extremely expensive. I am getting frustrated with his lack of progress and I don’t know what else to do.

Does anyone have any experience with this? Any advice at all? I am feeling so hopeless and not at all good at this.