I Jailbroke my iphone a year back.
My Laptop was formatted a month back and now i downloaded new itunes.
Will i Lose data(Contacts/messages/pics) if i sync my phone with this new itunes?
If yes what should i do
I haven't heard of anything like that happening unless you restore the phone, and simply plugging in your iPhone doesn't sync it, unless you have it set to automatically sync when it's plugged in, and in that case you can just cancel the sync.
If you're really worried just make an iCloud backup beforehand, that'll backup the aforementioned data (pics, contacts, etc)