What Causes Abdominal Pain With Diarrhea With Mucus In Stool?

i have had mucus on and with my stool, stomach pains, different stools diareah and old looking harder stool. tomorrow will be three weeks. i went to my Dr. last tuesday he did a rectal exam to check for blockage but didnt feel any. He thinks i had or have some type of stomache infection but didnt start antibiotics or anything. My stomache pains come and go and are pretty strong when they come and I have had mostly diareah the last few days. My Dr. told me to take metamucial and i did fow a week now. I called the office again Fri about the cramps and they told me to take pepto so I did that today all day but it didnt help