Hidradenitis suppurativa under my arm causing awful breast and shoulder blade pain. is that typical? i can barely sleep anymore.

Maybe: Pain and irritation are more commonly at armpits, the area involved. But the scarring tissue may make pain and irritation extended to surrounding areas.

See dermatology: you need to talk with your physician about seeing a dermatologist.there are treatments now for it such as Remicade (infliximab) or other TNF inhibitors that can be very effective. Ask your physician to help you get the appropriate therapy.