I Am A 48 Year Old Man. I Started With

I am a 48 year old man. I started with a mild amount of blood in stool about 4 years ago. I had a colonoscopy by a specialist back then and he diagnosed me with mild ulcerative colitis. It has never bothered me. I feel o.k. Early this week I passed a large amount of mucus with traces of blood in it. Thought it was a fart until I checked my underwear. Should I be concerned and go back to the specialist? Or is it just the ulcerative colitis acting up?