I went to the dr 2 weeks ago because i experienced problems in my rectum/anus. when i sitdown its painfully. i have no piles. it feels inflamed. i was on antibiotics for prostate inflammation but that didn't cure the problem. what can this be..i'm only 38

Anal fissure: You likely have a tiny tear in the short distance from the outside (the anus) /inside (the rectum). This short (1") length is the "anal canal" encircled by 2 strong muscles "the anal sphincter." a very tiny tear in the lining of the anal canal creates severe pain before, during, and after a bowel movement, "like passing glass." it may feel you're sitting on a golf ball. See a rectal surgeon.

Several things: Just because there isn't a pile, it can still be a fissure. Pile comes after long standing fissures. It can also be a sexually transmitted disease. It can be an infection. Make sure you continue to follow up with your physician.