HELP.. Very sick clown loach.

Tanya Member Posts: 2
My clown loach initially showed signs of overeating and bloat. Started 3 days ago. Overate bloodworms. Now it seems it is in a lot of pain. Not swimming and curling it's body around. Seems to shake when moving. Even popping it's face barbs out which looks like pain reaction. I fed some peas on day 2 but not sure if it ate. Belly has gone down a little but still seems in pain. Still showing color but slight grey in black area. Performed water changes every other day. Water parameters good. Ammonia:0, Nitrites 0, nitrates under 10ppm.
Tank is 40 gallon, heavily planted with wood. Tank been set up for 3 years so well cycled. All other fish okay. Might put in qurantine tank tonight. Is it constipation or worse?