My chicken is sick - standing still, tail down, eyes opening and closing.?

It started a week ago. Shes' a lively chicken, one year old. One afternoon, she stopped walking around, tail drooped, shuddered a bit, then her eyes closed. I took her back to the coop where she slept for an hour or two, then drank a ton of water, then went back to sleep. Next morning she was herself again. Now it's happening again... Also, some of her eggs lately have looked really strange. A papery translucent shell, with a string of papery material at the fat end, looking like a dried umbilical cord. Any help is appreciated!