What does it mean if I have rare but chronic anal spasm and bleeding?

[Joestew]

I thought when I was 13 that it was because of intense wedgies or maybe because I began masturbating too much, but even to this day, something flares up.

I'm 20, male, sexually active but nothing really envolving penetration of the anus, no blood in my stool but fresh blood, I assume from something more near the aperture.

Sometimes it feels itchy, others fiery. I'm lactose intolerant but I eat cheese, but I'm vegetarian so nothing I eat is too heavy really.

I don't know whats important information for this problem, any help would make my life exponentially better, thanks.