It wasn't that Harvey thought about sex all the time.
Harvey thought about winning all the time.
As competitive sports went, sex wasn't really great in terms of discerning who had won or lost. There were too many variables. But, on the other hand, it wasn't a bad way to pass the time when not winning: sweaty, filthy, athletic, moaning, writhing --
Harvey did think about sex. Vividly. Just...as a sidebar.
And there was a certain sense of triumph in taking someone to bed. Plenty of people had made passes at him, been the aggressors, but Harvey preferred a challenge. He liked to be the one to chase.
When he was an ADA working for Cameron, so far back when, he'd never considered Donna someone to chase, because Harvey was a professional. She was the ultimate unattainable -- she'd never have slept with him -- but Harvey wouldn't have done her the disservice of making a play, either. She was worth more to him than that. (If once in a while he had private moments with his hand and the thought of her long red hair, well, you couldn't prosecute a guy for dreaming.)
The fact that his mentor, his hero, hadn't shown her the same respect was what tipped Harvey over from doubt into action. Had he known Cameron was making Donna uncomfortable, had he seen it for himself, he would have put a stop to it (potentially a career-ending stop with a right hook to Cameron's smug-fucker jaw) but Donna didn't want that.
Somewhere between Harvey's first day when she'd taken him under her wing and his last day when he'd walked out with his arm around her shoulders to show everyone that she wasn't being driven out, she was leaving with him, what Donna wanted had become of paramount importance to him.
Also, she knew about his thing with his fellow ADA, Clayton, and she'd never once been mean about how Harvey, slick ladies' man, went mortifyingly tongue-tied around him. The guy just smelled really good and was smart and attractive and all he'd wanted to do was push Clayton down over a table in one of the claustrophobic meeting rooms and give him a blow job.
But Harvey's one youthful attempt at a boyfriend had made it barely past groping before the other kid got scared (of the world which was unkind to gay kids, of his parents, maybe of Harvey's arrogance) and broke it off. So he was not, per se, experienced in these things, and buying books or learning from porn wasn't really an option when you worked for the State of New York. Plus Cameron had always said -- and Cameron did have useful advice to give -- that there was no teacher like experience.
He'd dreamed about Cameron, more than once, but he'd made sure never to let it interfere with the work.
Harvey was an ADA for the State, and then suddenly he was a gunslinger at Pearson Hardman. Neither position was one in which he could have gone to a gay bar without a fair amount of trepidation.
So he stuck to women, which was fine, because he loved women -- loved their eyes and breasts and asses and legs, loved sex in any number of positions, liked high heels digging into his thighs, the way they moaned, sharp fingernails raked down his shoulders.
But once in a while he'd catch the eye of one of the male associates, or one of the partners (all men but for Jessica) and think, I'd hit that so hard his last ex would need a cigarette.
He sublimated it into admiration -- of their clothes, of their lifestyle, of the expensive liquor and shiny watches and hot dates. He was never entirely successful, but at least it kept him from pulling another Clayton. He grew into himself. He grew up. He got over it.