It is hard not to hear about website data breaches. 100 million records from this site. 300 million records from that site. I typically cross my fingers and hope that my email addresses or usernames aren't included in these publicly acknowledged breaches.
However, I found a website, Have I been pwned?, that aggregates usernames and email addresses from such data breaches. Try out the website to see if your usernames or email addresses may have been compromised.