Am I in love with my best friend?

Ive been straight all my life. I'm seventeen and have had boyfriends before and have been in love before so i know what it feels like... Ive been single for more than two months now and have recently started hanging out with one of my friends, who is a lesbian. Were pretty close, and I'm sure i can call her my best friend now. i feel super comfortable around her, a level of comfort Ive only felt with either family or the people Ive dated. Whenever I'm not texting her or with her i have the lingering feeling that i miss her. We hang out whenever we have time, and she said she really wants us to hang out this summer too. The catch is that she has a girlfriend and they're very in love... and i don't even know if i like girls. I mean, Ive been pretty lonely the past few months, and all of a sudden Ive started to notice how attractive girls are. I don't know how i feel about it though, and i still like guys. Besides, I'm definitely not the type of person to intrude into a relationship, i could never, would never, do that. Also Ive never really had a best friend before, so are you supposed to want to be with them all the time? Please help, and i know this is a super long question but i have nowhere else to turn... any help is appreciated :) thank you