Iphone help! All contacts are gone

OK, so I went ON my papas computer and I downloaded some of his songs from itunes on to my phone. Now I have all Of his songs but all Of my contacts are gone and I have all of his. I also have all of his pictures and none Of mine and all Of my Old messages are gone.

Um if you used his itune account than sometimes when you sinc it, it transfert to his things