Supposing you don't have a server, no worries, no virus, but unfortunately your are victim of a "Joe Job" or email spoofing.
The worst is that your email can be blacklisted by spam filters from your contacts.
The one thing I would do is notify your ISP that you're having this problem, if you use an ISP email address.

To be sure nobody is using your account change your password.

Verify if your antivirus is up to date and if it is effective to detect spyware.

The last desperate action would be to change your address email.