I lost all my new data on my iphone

I got a new iphone5 for christmas. In january I put it into my computer and it backed up all my pictures and messages and contacts and all that stuff into the computer. I hadn't backed up my stuff on the computer since then. In April my phone fell in water and I got a replacement phone. I had forgotten that I backed stuff up on the computer in january so i just decided to start over. Today, i put my new phone into the computer and itunes asked if i wanted to put my old stuff into my new phone. I said yes! I thought it would merge the new stuff and the old stuff BUT INSTEAD All MY OLD STUFF IS ON HERE AND MY NEW PICTURES ARE GONE. MY IIIIIMMMMMPPPPOOORRRTTTTAAAANNNNTTT CALENDAR EVENTS ARE GONE. MY MESSAGES ARE REPLACED WITH MESSAGES FROM JANUARY. MY HOMESCREEN PICTURE IS CHANGED. Can this be reversed?
Please TELL ME IT CAN BE REVERSED

It used the last known back up.iCloud anyone? It backs up every night over Wi-Fi if you set it up. It's FREE. Your probably using iPhone on windows, right?