Apologies for the late reply, but maybe I can still help 🙂
You should look on the receipt you got sent to your email address. This should say the username with that you subscribed to Spotify premium! Try to log in with that account. When you see a 10 digit number log in with Facebook!
Have a great day!
Help others find this answer and click "Accept as Solution".
If you appreciate my answer, maybe give me a Like.