Sexual obsession is a tricky thing to put on film. You can reveal all the flesh you want, yet how do you get an audience to experience, vicariously, what's going on in the mind, the heart, and...other parts of your protagonist? In I Am a Sex Addict, the writer, director, and star, Caveh Zahedi, turns filmmaking into confession, acting out his own erotic memoir, and since what he tells us isn't pretty, the film carries a grubby, sensational conviction it's hard to turn away from. A tense, squirrelly man with big white burning eyes that make him resemble a gnarlier Fisher Stevens, Zahedi speaks directly to the audience, then goes back to recall and reenact his relationships, exploring the addiction to prostitutes and the compulsive honesty about it that destroyed, over and over again, his love life. His biggest delusion is that his 1960s-style ''openness'' was anything but veiled hostility. Yet when it comes to revealing the twists and turns of his libido, Zahedi is ruefully funny and savage in his self-exposure. He shows us how sex, for him, became a refuge, a packaged escape, a drug posing as a force of life. I wish that the actresses playing Zahedi's wives and girlfriends weren't so L.A.-model sexy compared to the real, earthy women themselves (whom we glimpse in home-movie footage), yet in one case, with Amanda Henderson as Devin, a free-spirited alcoholic whose problems, for once, matched his own, Zahedi demonstrates that he's a diary-film maker who can transcend confession and its lurid cousin, exhibitionism, too.