Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain it seems that hard red/blackish bump on your butt, near the crack with red or yellow and green scab touch, seems most probably be due to formation of a Perianal abscess that has formed a thick layer over it due to continuous friction and irritation turning into a scab.. It occurs most commonly due to hairfollicle infection while other causes can be infected gland in the area or infection in the skin leading to pus formation under the skin.. As it is persisting and keeps on growing and reducing in size you need to get proper oral and topical treatment for complete resolution.. I would suggest you to consult a Proctologist or Anorectal surgeon or you can even see a general surgeon and get evaluated. He can advise you a course of antibiotics, anti inflammatory painkiller and topical application of antibiotic, steroid and numbing ointment.. Do warm compresses as it will help in making it smooth and can ease in draining it off.. If it still does not improve or start worsening then Incision and Drainage can help in faster resolution.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.