Dog coughing for weeks

Rottweiler, male, intact 120lbs 7.5 years. No history, always been healthy.

Dog started coughing roughly 3 weeks ago. Took him to the vet, they didn't give him enough sedation and he was fussing so they couldn't take the x ray. Sent us home with antibiotics.

2 weeks later, almost end of antibiotics & hes still coughing but seems fine otherwise, is eating normally and wants to play.

Can't tell if its getting better or worse, sounds about the same. Wheezing cough with unproductive terminal retch, sounds like fluid in the lungs that won't come out.

Called the vet again this morning they said to bring him in and we'll try a different method to sedate him for the x ray.

At this point I'm thinking its probably something serious since it hasn't cleared up on its own and antibiotics didn't even help.

So I'm wondering is it worth the ~$1000 vet trip. He doesn't have insurance and if its CHF or cancer or something horrible like that I don't have the money to keep up with the treatments anyway.