This is called Display Name Spoofing. Someone acquired a list of contacts and the email display name you use to send email. They sent an email from their own email address, but changed the display name in the 'From' address to your name, making it seem like it was coming from you.
For example, the sender could be Darryl Dodds<123tech@spammers.com>
...where Darryl Dodds is the display name and 123tech@spammers.com is the email address.
… This means the email account has not been hijacked and is not being used to send the email. The email address indicates it's an account that is not from your own server.
They can harvest your display name and contacts from emails you sent out before to anyone, from facebook, from colleagues who've had their mail servers infected. It's really not possible to find the source of their information.
This type of spoofing has been around for a long time, and continues to be a popular method of delivering disguised email. Since the 'From' email address is legitimate, and mail servers typically ignore the display name, they think it is just another email and allow it through. There is very little that can be done to block it.
Here's an article that explains it as well: https://www.itro.com.au/display-name-spoofing-latest-scam-technique/
For those who contact you about this, get them to look at the 'from' email address, not just the display name. They can then block the email address if they like by designating it as spam.