Yes. Many years ago with BF2.
But limitations are limitations.
He wants to marry. You do not want to marry him.
It is what it is, so the relationship has to change shape.
Hang in there as you grieve for the loss. Not of HIM - but the romance. It will get better.
And you have a great friend to boot! That's nothing to sneeze at. His being around still as a good friend, and friendship is a precious thing.