His difficulty eating was the result of his having an RI...do take him to see the vet a.s.a.p. (thank you!) I guarantee he had this before struggling
to swallow that mouse...but his symptoms were subtle & you just hadn't noticed before that.
Snakes have the most amazing physiology in that they can breathe easily even while swallowing whole prey items; what they cannot do though is
cough up secretions that block that tubular structure that allows them to breathe while swallowing.
I hope he makes a quick recovery...being unable to breathe is miserable for a snake & nothing to mess with.