Hi - I too suffer from proctitis (mostly) but also some left sided issues. It is horridly stubborn & for me -- when I asked my GI about
the pain while sitting & he gave me Flagyl. Must say that within 2 days the pain was much better. SOoooo in my case moderate to severe pain while sitting (typically accompanied by aching down the backs of both legs) in my case - these are indicative of needing an antibiotic.