if you google image hormone cycle of a period, theres this great 4part pink graph thing that breaks it all down and it makes sense. days 24-27 into a cycle you may weigh the most because uterine lining is at its thickest, and pituitary hormones at their lowest/sex hormones are dipping down. remember to be gentle to yourself. Progesterone slows down digestive system and creates water retention, which is where some of the weight gain comes from.