Severe neck pain, muscle spasms , jaw pain, difficulty swallowing

My son is 8 years old. I don't really remember how it started but one day after he went to " Urbina Air “for a friend birthday he had a fever at night and symptoms like fu. I though its COVID and I tested him but he was negative so I gave him Tylenol " just for one time). Next day in the morning he woke up and the fever gone and he was fine. One day later he started to complain from his neck. At the beginning I didn't pay much attention. I thought he slept wrong and it was something temporary. Two days later when he continued with the pain, I took him to urgent care. They couldn't find anything wrong with him. One day later I took him to the emergency room. They did CT on the neck to rule out infections and abscess. They found out: Prominence of the adenoid and palatine tonsils. Prominent level 2 lymph nodes bilaterally measuring up to 9 mm short axis are favored reactive.
They gave him antibiotics and said in two days he should feel better and to continue following up with ENT. A week passed and he still didn't feel well. When we went to the ENT she said she doesn't know what is wrong with him and she asked to take him back to the ER . We went back and this time we got admitted for two days. They did an MRI and changed the antibiotics and gave him painkillers and one dose of steroid. He felt great with the pain killers ( IV) and the steroids. The MRI showed the following: Mildly enlarged lymph nodes in neck. there is asymmetric prominence of the right lateral retropharyngeal lymph node. The tonsils are also middy enlarged. No collection or mass lenition is identified. Everything else was fine
We got discharged from the hospital and he was fine for just two days then the pain came back again and has been going continuously for more than two months now.
He currently has severe neck pain with trigger points at the back of his neck and severe neck stiffness and swelling around his neck. He also gets a headache that starts from the base of his neck and travel to the head from front and pain in his ears. His head tilted forward and his throat mules get very very tight to the point he get chock while eating and can't talk or open his mouse widely.
He feels better in the morning when he wakes up or when he lay down only.
We went to ENT, neurologist, orthopedic, and pain management and PT. No one knows why he has these symptoms I really don't know what to do. Our life turned upside down and he became completely homebound. He only goes to doctors for medical appointments and PT 3 times a week. Any idea what is this could be