I have rash on my butt that doesn't go away. Also at times my rectum itches so bad. What can this be? The rash is on my right butr cheek looks dry but at times flares up and feels like bumps. My rectum sometimes itches so bad & my vagina at one point itch

Number one cause of. This, pruritus ani, itchy butt, is excessive caffeine. Beer also tends to make this worse as does excessive perspiration. Stop all caffeine and beer and use cornstarch powder liberall to the area several times per day and at bedtime. Caffeine classicly causes the itching especially if it wakes from your sleep at night.
It . It sounds like you may be dealing with a fungal infection. You can try an over the counter anti-fungal cream like clotrimazole. Apply it to the affected areas twice a day. You should also use a vaginal cream like monistat or gyne-lotrimin. This should be inserted into the vagina nightly for 3 or 7 nights. If you do not notice an improvement then you should see a medical profesional for evaluation and treatment.