I was almost raped

I'm sorry, this has been bothering me and I didn't know where else to go as well as I didn't know where to post this. 

What happened was I dealing with a dude and we have had consensual sex prior to this happening. But basically dude is a famiy friend so he is always over my house and one day he just popped up as he usually did. It was just me and him in my room and it started out pretty normal. I was just laying on my bed and we were talking. Then he started touching on me and I really did not want to have sex that night, so I said no. 

Dude proceeds to try to touch my breasts and I continue to say no and brush his hands off of me. He usually tried to convince me but after a second firm no he would stop but that night he didn't. He basically pinned my wrist over my head and shoved his hands down my pants and said just let it happen. And I honestly think that had my dad not been home and had I not been loud I would have gotten raped that night. 

I'm 19 and I'm engaged. I haven't told my fiancé about this situation because he already doesn't like this guy due to something unrelated and I feel like if I tell him or my family they might try to kill this kid. I honestly just don't know what to do and I don't know why this memory chose now to show it's self

EDIT: I didn't add, I'm a decent sized girl but in height I'm only 5'4, this guy is 6'0 and 230+ pounds so it took me alot to get him off