painful/rash/itching? please help

For the past 3 weeks I have been experiencing some pretty bad anal itching, from the rectum up through the entire crack. I noticed its a bit red and at times feels cracked to the point where it appears cut. I had been applying neosporin for a while and then decided to purchase caldesene baby powder. That seems to be working a little better however I am still very itchy and my crack is still pretty red. I have also been experiencing some intense stinging/stabbing pain during bowel movements resulting in bright red blood on the toilet paper (been going on for 1 ½ weeks). Here are some of my theories of what it could be. I have narrowed it down to HIV (yeast infection), herpes and hemorrhoids.  I'm hoping hemorrhoids but im having trouble thinking its that because its been going on for so long.