That's common to end up with multiple accounts. First LOG OUT of whatever TurboTax account you're logged into right now. Then use this TurboTax account recovery website to get a list of user ID's for an email address. Run the tool against any email addresses you may have used
If you used the Desktop CD/Download program then the only copy is on your computer and not saved or stored online.
If you can find your 2018 return but can't open it then click on Add A State to let you back in.