Why do i feel the best a week before and during my period? after, i am nauseous, fatigued, can't think straight & bad ha. i have a pituitary tumor fyi

Interesting symptoms: Would need more info, including whether the pituitary tumor is secreting or not. At your age, it would most commonly be a prolactinoma, but your symptoms would seem to fall in line more with an acth secreting or gh secreting tumor. If not secreting, then hard to explain symptoms. All of these tumors, however, are treatable with either surgery, radiation and or medication.

Cyclic malaise: This is complex. Because the symptoms relate to the m. Cycle, and there is a pituitary tumor, symptoms are likely related to hormone levels. This would require a thoughtful, compassionate doc who would measure levels at different times of the month and adjust hormones accordingly. Endocrinologists are most educated here but may not be interested in you. Your pcp may be more helpful. Space ltd!