What does it mean when i'm discharging pus from my anus and it's very foul?

You have an anal infection from various causes. You need to see a PROCTOLOGIST or your internist for immediate treatment before the infection spreads. Possible causes, hemorrhoids, trauma, perianal fistula and an STD.

Several possibilities include perirectal abscess, other intraabdominal infections with rectal fistula, inflammatory bowel disease (Crohn's disease or ulcerative colitis), and STDs, especially gonorrhea or chlamydia (if at risk for STD). See a doctor ASAP. Good luck.