You're the only one who have access to the wallet ?
Yes only me have access.
How can someone hacked blockchain.info wallet... Nice..
there could be lot of reasons
1) your device was infected with malware or malicious things
2) you click links that are possibly phishing or links with keyloggers
3) you left your wallet open
4) someone knows your passwords and identifiers
**
its better to not use your device,computer, or whatever you're using.