SUBREDDIT: r/relationships
TITLE: i'm [20 M] extremely uncomfortable with my girlfriends sexual history, how can I get over it?
POST: First time redditor asking what has probably been asked a million times, who cares.

Met a girl at uni and now we're together (hasn't been very long since r'ship started like a month maybe). Had sex a ton but not much else.

I guess I can be a bit jealous/particular about my partners idk. she's only had sex with one dude and she's always adamant self respect is huge for her and that was something I was attracted to in the first place. 

Then last night she sprung on me that she's had a threesome with some dude she met at a club and a good female friend of hers (my gf did everything but have sex but her friend did). I freaked out a bit and she lied and said it was a joke but this morning she said she it wasn't a lie she was afraid I would end it with her. 

I'm super super super uncomfortable about it and I can't really get it out of my head or shake how slutty it is (I'm definitely not a one night stand kind of guy) 

Am I overreacting? how can I get over it? should I end it? 

thxthxthxthx
TL;DR: 
gf had a threesome kinda and i find it really slutty/weird shall I end it with her