How I [F]inally got a threesome with my BF [M] and his best friend [M]

My BF and I have been together for almost 5 years now. We're both 23, and we just got engaged last weekend. Because of this I will be referring to him as my BF because this story happened when he was still my BF, and not my fiance yet. We both trust and love each other 100% and we know every little secret about one another. Because of this, throughout our relationship we've both had "freedom" for a few nights. Basically meaning we got to do whatever we wanted as single people. We always told each other afterwards everything that happened, and I believe we are so much better off for it. I hadn't had sex with anyone else besides him, and he had sex with one girl long before our relationship started. Those nights of "freedom" we're used primarily for dancing, drinking, a few make outs, etc. The farthest either of us had gone was he had gotten a hand job and a few guys got to finger me.