Does it mean one has been hacked if you get spam from yourself in your email?

No. Spammers can put any name or email address in the "sender" field. They can programmatically enter your name or email address as the sender, or even Santa Claus. This does by no way mean that your computer was hacked or accessed by other people. The reason they do this is because it increases the likelihood that you will open the email and react to whatever they are advertising. People are more tempted to open spam emails when it comes from someone they know, or particulary when it seems to come from themselves. The only real way to know where the message came from, is to check the email header and to track down the IP address of the sender's computer.