Do my nipple suppose to have discharge and be big and black while im on my period?

No discharge. Discharge from nipple must be investigated cytology from discharge should be done mammogram may be worthwhile.
Exam. Get breast exam, doctor should check for blood, prolactin, possibly mammogram. Discharge on both nipples, with expression (squeezing, not spontaneous) & non-bloody then to be bening or normal variant. You need to see doctor.