What Causes Burning Sensations In The Rectum And Penis Tip?

Quite often and randomly will get a burning sensation in my rectum and around the tip of my penis. I was told I suffered from prostaitis and it was never enlarged. The Doc tried sveral meds from different families but I typically have neglected taking any due to the foggy feeling they give me in my head for several hours each morning usually into the afternoon. If there natural remedies I could try to limit this to a degree? I already take saw palmetto which really helped my bathroom issues. Also I've been noticing my erections are weaker these days is this due to my prostate?