I was on the Depo for a few years, too. Prior to that, I had the Norplant for five years. I don't remember my sex drive being as affected with the Norplant, but back then I was also twenty-two-years-old with a kicking body. Shoot, that alone was enough to get me going in those days. Ha ha... but I digress.
Anyhow, I just wanted to mention that I tried Viagra once, too. It gave me headache. But I also experienced another weird side effect - everything had a very different hue to it. No, not me. LOL But my vision. It's like I saw the world with an odd blue wash painted over it. And not in a groovy psychedelic sence, either. It was just creepy.
And no, it didn't work for me, either.