Fruit juices or honeyed water can be useful for keeping your energy up. Also ice-poles or barley-sugar sweets. And if you feel sick but have low energy still try to drink/take a little something - i know it's off-putting when one feels sick but throwing up is the worse case scenario and actually that can help open your cervix up.
Water is a great way to relax you and ease the pain. Eat some protein early on to keep up your strength. Fruit juice throughout helps too. My labour was not progressimg so our wonderful midwife had me walking around doing a weird walk, lifting my legs up to the sides and had my husband doing nipple stimulation (sorry if TMI!) which really helped to strengthen my contractions and speed up my labour. She was getting worried when I hadn't dilated any further from 5cms in a few hours but after doing the walk and the nipple stimulation I was fully dilated in another 2 hours! I also used Bach Rescue Remedy which helped loads.
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