@Horny boiI'm really not sure that my own story qualifies as 'a ton of sex' (though the amount is creeping up, perhaps), but that's in the eye of the beholder. I'm prone to having one reader say 'there's no sex!' and another saying 'it's all sex!' so I'm not really sure what any particular reader will think.
That said, coming of age (in an unusual way) certainly fits, and it's pretty much all character-driven, so:
https://storiesonline.net/s/20679/variation-on-a-theme
Many of Aroslav's (already recommended by someone else) certainly fit.
Also, Michael Loucks' A Well Lived Life fits everything on your list: coming of age, high school (and college, and adult life), quite a lot of sex, and well thought out characters.