Hi,
Your sister is likely correct. Had that same issue when I was younger. You can also place yourself in the f zone too.
My advice is to communicate more, be bold make a move here and there on a guy you're into. Work on your self esteem and, or confidence. Many of us dont really figure out dating. And many of the guys that are looking for more than one thing get labeled as nice and shoved aside for the semi charming jerk etc. Try to be patient as you look around for what is out there.