Put up some pics of it now.

And looking at the geometry page for these frames.....The 51cm you got is measured from center of the BB to the top of the seat collar, not c-c or c-t. That's a tiny bike. It's probably something like 47 cm c-c if that is indeed how they are measured.

But if it feels fine, who gives a ****. I'm 5'10" and ride a 52cm c-c frame. So we're in basically the same ballpark as far as frame size to rider size goes, and I'm fine with my bike.