I don't think you were hacked. It sounds like a computer virus that is spoofing addresses.

Update your antivirus software and do a virus scan.

Also do an adware scan using malwarebytes

And for good measure, run Dr. Web's Cureit.

Delete everything that each finds.

 

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi