Any Tips?

I posted a little while ago about my son starting daycare for the first time in September and being constantly sick since then. Not much has changed except for now at night when he lays down he has post nasal drip that sends him into a coughing fit in the middle of the night. He coughs so much that he ends up gagging and then the gagging leads to throwing up. We are utterly exhausted. Last night we were showering at 2 AM. Has anyone dealt with anything like this and have any tips on what to do at night time? I put a humidifier in his room and use saline spray but nothing seems to help. I’m starting to wonder if it’s acid reflux or maybe allergies. I feel like I’m back in the newborn stage. 😴😴