After a shy snake (like a BP) has eaten, they're slowed down from the meal, & since yours is essentially out in the open (not in a hide!) with a big monster staring at him (that would be you ) I feel quite safe in saying that's why he was breathing heavily...& no, don't rush him to the vet unless you want to make it WORSE + have him throw up the meal he just had.

Get him hides that he likes & will use & try not to loom over him when he's in such situations (feeling slow & exposed). Remember snakes are mostly not able to identify us with vision alone (!) like thru the glass, so try to avoid scaring him! You could (should) have put a towel over his cage for a while, under those circumstances, or taped some paper over the glass to block his view & help him to feel safe (hidden).

He looks fine to me, btw. And yeah, stop being so "paranoid". We all have those moments of being unsure but I hope you manage to sleep better in the future.