At least you know ahead of time that you had feelings for him.
I did the fwb thing because I didn't have any feelings and I was under the impression that he didn't either.
Now he won't speak to me and the only conclusion I have is that it meant something more to him.
So, I lost the possibility of a great friend because a physical attraction got in the way.
I guess, my advice would be...Stay away from the physical.
People always end up hurt in the end.