The only two wrestlers to beat Cena clean at wrestlemania were The Rock and The Undertaker.
His other 4 losses came in a triple threat (he was not pinned), a singles with austin theory (austin tapped), a "match" with bray wyatt (that wasn't a real match), and one to the Miz, which was actually a double count out but the Rock restarted the match then screwed Cena.
So he is 10-6, but if you don't count the cheap wins he would be 11-2.