darn it I just replied on phone but it didn't post.
Ok, I'm guessing you might have an eggbound hen. That means just what it sounds like. You are going to give her a nice, warm soak in water. If you have epsom salts, add a cup or so to the water.
You can use your kitchen sink, a big plastic storage tub, whatever. Get towels ready, and a blow dryer for hair if you have one. Put her in - water should be fairly warm but comfortable. Deep enough to cover her vent when she is laying down. You might have to hold her down, but most will settle down soon and relax. Keep her there for 15 - 20 minutes. You might have to add warm water if it starts to cool down, you do not want her to chill. If she starts to pant, she is overheating and you will need to add a bit of cool water.
This is a good time to use your fingers to gently get rid of any poop stuck to her back feathers. Also watch for mites/lice. Key here is you want her relaxed, so move slowly and keep it as calm as you can.
When done, blot her dry with towels - you can wrap her in towel - and then blow dry if you have one, keeping your hand in the airstream so you know if it is too hot on her skin. Then when she is as dry as you can get her, put her somewhere warm and quiet.
Then, google eggbound, and then , start a new thread so we don't drive everyone nuts here who wants to be reading and discussing mareks issues. I hope you report back! it could be something other than eggbound, but it is something to try.