Why do i have such a huge urge to experiment with my best friend?

Well its more of like one day its a strong urge, the next day theres kinda an urge there and another day there really isn't one there. Anyways i dont really know my sexuality since i never really liked either gender (i thought i did at some moments but really it was more of a teeny clingy atttaction, not a crush) so i label myself straight yet idk my actual sexuality. So anyways my best friend did want to touch my boobs this one time while we were hanging out at her house and i let her, and it kinda felt awks but i sorta enjoyed it. I brougt it up like a few mknths saying i really enjoyed it, though she said she was ytying to forget about it just becuz. So this one time my best friend made out with our triend, but after she told me it was gross becuz she felt her moustache lol ew and it felt odd. I mentioned this one time if we could experiment ( as on makeout) and she kept on saying she didnt want to because shes done more things with girls then with guys and she said she was more attracted to guys even tho she told me she was bi ( but becuz she had this attraction to boobs not females themselves, thats why she wanted to touch my boobs). Im gonna say this nice and clear that shes the only person ive donw anythibg physical with ( in my mind i would only do something physical with someone if i liked them, but i was curious to see how it would feel soo...), yet i know i wouldnt regret being curious with her, the reason unknown. I know this one tume we were mad at each other becayse of something stupid and we dudnt relly talk for like a few days or do anything, and i remember when we saw each other while walking ti school i ran up to her and hugged her reallu tight for a long time because those few days suckeddd without her!!!! I remember like 2 times i had butterflies when i was with her bjt they kinda faded after time. What do u think i should do? Shes a lot more independent than normally us so hanging out would be hard. What should i do ???? Im 15 soon 16 shes 16 ty