What does being in love feel like?

I had never experienced what people described as "being in love". I've had crushes and flirtations and that's it. And I used to wonder how anybody could be so sure of another person to exclusively be in a relationship with them. But recently I felt that with my bestfriend. I know it's not going to be reciprocated, but I cannot shake this feeling off. Am I in love with him or is it an obsession or something?
What does being in love feel like?
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