Why don't guys come up to me?

Ok so every time I go out with a group of friends guys don't come up to me! I'm not ugly lol but lately I've been the third wheel or if I go out with a group of girlfriends I still don't get hit on or even really talk too. I have to buy my own drinks ! Lol but when I do go out with gfs they are normally a lot bigger than me and I feel like I'm prettier but I don't act like I'm conceited where guys wouldn't want to talk to me I don't understand why
Why don't guys come up to me?
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