Is it web-based email or is it an email client like Outlook?
If the former, it is likely that your machine is compromised, not your account.
The latter, it is probably your account.
Check your sent folder, can you see the emails in there?
If you can see them, then it is unlikely that you're being spoofed. If you can't, it either means you're being spoofed or that the person who has subverted your account is deleting items from the sent folder after they send them.
Best bet is to log in from a different machine and reset your password.
As for cleaning a compromised machine, you are not going to have a good time of it.
Using Windows? Try
Windows Defender free from Microsoft.
You'll also want to make sure the
Windows Malicious Software Tool, also free from Microsoft is installed on your machine and your machine is up to date on its software updates from
Microsoft Update.
Doing that and making sure your cookies, temp files, and internet history are cleared is important.
You may also want to consider using a different browser (like firefox or chrome) if you are currently using Internet Explorer.
Short answer, clean your machine, update your machine, use a different machine to change your passwords, and give us a little more info.