How is tracheal collapse diagnosed? Xray?

I have an 11 year old Pom. I adopted him when he was about a year old. He’s always been a loud mouth breather and snores in his sleep. Back in December I noticed he started a little cough. Like maybe twice a day. Figured it was just from the changing weather (got hit with some really cold weather we’re not used to). Totally fine otherwise. Eating/drinking/playing normal.

Brought it up to our vet in early January and they said he seems fine. They felt around his throat and listened to his heart and lungs with a stethoscope. They said if I was really worried we could try and do an xray, but they didn’t think it was necessary. It’s now march and he still has this cough, it’s maybe 5x a day now. First thing in the morning and then anytime he gets too excited. Still same eating & energy levels. I just feel bad!

The vet quoted me $600 for the xray, but I’m reading online that the xray will only work if he’s experiencing the tracheal collapse at that moment?

I just don’t want to throw money down the drain. Or maybe I should just go back in and see if they have medicine to treat a cough? He doesn’t get along with other dogs and therefore doesn’t hang with other dogs, so I think kennel cough is ruled out?