Personally I think it is not common for someone age 16 to do that, but at the same time I think it is more common that people would suspect. Sixteen year olds are filled with hormones and their sexuality is kicking up into a different gear. At the same time sixteen year olds have undeveloped temporal lobes. Their rational thinking and self-control hasn't fully come online yet. That is precisely why many societies do not hold 16 year olds legally accountable for their actions. They are not fully developed - they are still kids.

The scenario you set - a sixteen year old driven by hormones exploring sexual behavior with an 8 year old is not the actions of a morally depraved human being but a 16 year old kid with undeveloped temporal lobes driven by hormones and lacking in self-control.

So you know... cut yourself some slack. I don't think you need to call yourself a sexual predator based on behavior from when you were a child. Besides... sexual predators don't throw themselves under the bus like this. Sexual predators do everything in their power to hide their actions and inclinations so they can continue to do them.

As I said... if you still lack the self control to not act on sexual impulses in ways that break the laws of your society as an adult, then get some help. But judge yourself of you level of self control now, and not that which you had when you were 16 years old.