If someone has your email address can they find out what sites you have accounts on?

I’ve been very careful to keep my current online usernames and information private. I let slip something I posted on a site to someone. Within 24 hours my account in a different site had a hacking attempt against it. I make a point not to share my email address but could someone get my email address from the first site then use it to find my accounts across the internet? Yes, I’m paranoid.

address email privacy