So I have an old minecraft account. But I need to use my email to change my skin. I have tried all the emails I could think of but it still didn't work. Is there a way to check my email that i used. P.S I use a Mac and I know my username and password
I would recommend you read through the "I forgot the email address used for my account" section of Mojang's support -
You can reset your password through their website and it will send an email to whatever account you have access to. This email displays which address is connected to your account, and allows you to regain control of your Mojang Account.
If all else fails, I would recommend contacting Mojang Support directly, who will be able to solve this issue -