unless you have a backup.
I dont have any backup of my wallet. I only have the private keys written. Am I safe ?
There are a lot of if's here, but if you're sure it's your private keys that you wrote down, and if you're sure there are no typos, and if you never add any new receiving addresses to your wallet, than you should be safe.
Edited to add: and also if they're either unencrypted, or you are sure you know their password.
Where did you get this number you are calling your private key? How did you get it from the blockchain.info web site?
I should not have used the word written as I have not literally written them down anything with pen and paper. I'm not very sure what encrypted/decrypted things u r talking about regarding private key. I have used only one address on blockchain.info and have downloaded the paper wallet, which is a PDF doc, from their wallet dash board. That PDF has the address and the private key written on it.