Hey Mikey, a couple of questions:
is there anything major you had changed (anything at all) with the tank over the last 72 hours?
what other fish do you have in the tank, and, are the other fish showing any signs of stress? (if the other fish are stressed, something is wrong with a parasite or water quality)
what kind of substrate do you have? (could lead to chocking, but this is rare).
Currently, is he breathing at a constant rate, or does it look like every couple of minutes he's "bucking" and trying to blow something out? (if it's this, then there's probably something stuck) or, is he breathing at a steady state with no change (means something else might be wrong)?
Can you see his sides? Do you see a sharp horizontal running along his side? (means he's emaciated and is severly worn out due to lack of energy)?
Has he stayed in the same spot this entire time or has he moved around, and, when he moves, is it an erratic flutter for a few minutes, then he just drops to the sand bed? (indicates he's stressed out from something)?
What is your ammonia/nitrite levels?
What is your PH?
What is your salinity?
Sorry you're having this issue. The good part is it's still alive, which means if there is something stuck it's not completely blocking his water passages.