Bill is your boyfriend

You and the other losers were having a sleepover at Bill's house.

The other losers were scattered throughout the room, and you and Bill were on his bed, you reading, him just lost in thought.

As everyone was getting ready to go to sleep, Richie looked at you, and raised an eyebrow, before a smirk came on his face,

"Damn Denbrough, nice job."

Bill's eyes narrowed,

"What're you talking about, trash mouth?"

Richie gestured to your neck, and on there, was a purple-ish red mark on your neck, just under your pulse point.

Bill froze, he left that on you when you were cuddling in the hammock, and he did not want you to know about that, as he left it secretly on purpose.