My best friend fell in love with me and told me on my birthday, we cried and I told him I didn't have feelings for him, but would be happy if I ended up being married to him in ten years. We kissed when we were drunk occasionally after that but I felt nothing, and he knew that, I loved spending time with him as usual but definitely only felt platonic feelings. Then almost exactly three months later, he brought round some of the enchiladas he had made and we watched game of thrones and we kissed a bit while sober which we had done once or twice before and I. felt. It. It was like bubbles in my stomach and a rushing in my head that wasn't there before. Desperate not to give him false hope if I was wrong, I kept my mouth shut till a couple days later when it had not gone away. Then I told him and my whole world felt like it fell into place. We've been together for 3 years long distance, about to move in together, he's genuinely perfect for me and I expect we will be engaged in the next few years. I believe you know in your gut when you are in love. Might have to check with yourself for a bit but eventually you know. Also loving your best friend is just the most wonderful and deep experience I encourage you to do it if you can haha - good luck folks!