I've been using data.exchange for a few months now, and I've always used the "Log in using Google" to sign in, but today, I used "Login using Stack Exchange" for the same email.
This option created a new user account for me. Then I thought maybe it didn't connect them to each other, so I logged out. But when I tried to log in using Google, I was logged in to my second account and basically I lost the way I could log in to my original one.
This is my first account: Profile
This is the second account: Profile
In short, it shouldn't have created a second user. I still need to be able to log in as my first user.