Suggest Treatment For Throat And Neck Swelling

I have severe swelling in my neck and feel the inside of my throat is swollen amd difficulty swallowing. This all happened after a root canal. I never had complications from a root canal in the past. I beem to the ER twice and they said my airways aren t blocked and oxygen is fine. They gave steroid injection and benedryl and morphine for the pain. It is now a few days of taking the antibiotics, steroids, and benedryl and swelling didn t go down in my neck and I still feel tightness in my throat and difficulty swallowing. Saw the dentist today, and he claims the tooth is healing and there is so signs of abscess or swelling right where the dental procedure was done. It s just swelling in the neck and throat and just on that side. The Er doctors told me to follow up with dentist and I did and he said he doesn t believe it is dental related and is some underlying medical condition the medical doctors are missing. He is not saying the dental procedure may not have caused whatever the underlying problem is to get worse, but he doesn t believe the swelling in the neck and throat is due to the root canal due to the gums or cheeks not being swollen. I am wondering if I have some kind of auto immune disease and the root canal made it get inflamed and my body isn t fighting the inflammation off or if it possibly is a thyroid problem because it feels like the area around my Adams apple is swollen, that whole side of my neck is swollen and the glands, I been very nausea and lost about 9 lbs in 2 weeks and I have severe tightness and squeezing feeling in my throat and it s very inflamed feeling and very uncomfortable and unbeatable to deal with. Wondering if it possibly is a thyroid problem and it got inflamed right after the dental procedure due to a complication with fighting the infected off.