6yr old complaining of difficulty breathing at night, but no wheezing or coughing - could it nonetheless be asthma?

[Solfege]

DS has been complaining of finding it harder to breathe at night / when he's lying down.
He's not coughing particularly, and I can't make out any wheezing I don't think.
Is it possible that it might still be asthma?
His dad had asthma until his early 40s, though not severely I don't think. I mention that in case it's relevant.

No one can answer this apart from a doctor