Would sleeping with your clone be viewed as:
B). Masturbation, or
C). Sex. Just sex.
Assume that said clone is close enough in age to you that sex wouldn't be weird, that the sex is completely consentual, and that you were not raised together (there's no family pressure). Plus, while your genetic makeup is the same, your outward appearence is not exactly the same—think that they have a different haircut, dress differently, have tattoos or piercings that you don't have, etc.
Strictly speaking, it would be incest—you're technically from the same parents, and your genetic makeup is the same—it would be like sex with your identical twin. However, since you'd be the same sex, reproduction wouldn't necessarily be an issue, and since that's probably the most taboo thing about incest, there wouldn't be all that much to worry about. So aside from the fact that your genetic makeup is the same, it would basically be like having sex with someone of your same gender, and yes, it would be weird, but otherwise, there would be nothing really "kinky" to it.
This raises the issue of whether you could have a valid relationship with your clone, but that's more into the environment vs. genetics argument—if you had a different life experience, would you be the same person or not? It's something to think about.
Yes, I realise that I posted asking about sex with zombies a while back. No, I'm not some kind of pervert—the zombie question was meant to be a bit of nonsense, and I wanted to start posting on a high note. :)