Chicken walking like a duck, not laying HELP

[Gusgus]

I have a 5 year old hen who started walking like a duck with her tail tucked under her and not walking a lot. When she walks it's very stiff, her legs widespread. She hasn't layed in a month. At first we thought it was egg bound, but we can't feel an egg. She eats normal, drinks normal, and we put her on antibiotics but no improvement. Her vent is red and swollen, and we've been giving her a warm bath every day since the problem started 5 days ago. Her poop is dark brown or green. Her eyes are not cloudy and she's not wheezing. Her abdomen seems puffy. We have her in the shop inside a pet carrier. We let her walk around a bit every day. Please help.

 

[Poultry parent]

despite the fact that you said you can't feel an egg, that sounds exactly like an egg bound hen