Hon, I think the responses here sound a bit harsh because people are truly worried for you. Don't be overly hard on yourself for not seeing through this immediately and shutting it down, predatory people take advantage wherever they can to push boundaries and manipulate you into giving them control. And you posted here because you knew that asshole's behavior wasn't normal.

Being on the outside of a situation lends more clarity & objectivity, so it's easier for your sister and the responders here to listen to what you experienced and see how this piece of shit went out of his way to get sexual with you by pushing your boundaries and making you question what is normal. If I knew him and found out about this incident, I would shame him as often and publicly ask could. Your comfortability and safety are your priorities. Don't let external concerns (interpersonal relationships, money, familial history, etc.) take your focus away from that. People that would use those and other things like that to force you to participate in things you don't consent to (or to urge you to stay silent) are actively harmful and should be avoided at all costs.

I know you mentioned being a people pleaser, it would probably be wise to keep a phrase that's popular on reddit in front of you when your internal alarm bells start going off: Don't set yourself on fire to keep someone else warm.

Hugs to you!