Someone is sending spam messages from my email!

A few days ago I received a few mails from my business contacts that I’ve been sending them some spam mails. It looks very bad on me to keep doing this, but I cannot find a way to stop it. I cannot make a new account because everybody important have this email address… Please, help me…
Answer #1
Well if somebody is logging in to your email account they obviously have got hold of your password.
So change the password! (before they do!)
Answer #2
These spamming email come probably from a place where you actually enter your email information somewhere , or that mean you have a trojan/keylogger on your PC
TSD have the solution , normally for that kind of case , simply change the password will solve the problem. And if it’s because of a trojan/keylogger , the problem will restart soon as you probably enter your information once more.