No, i didn't just forget my username and password.
Although my account is set to stay logged in, Minecraft did another spontaneous request of my email and password to login, and ive never had this problem before, but using the same regular email and password as always, and i was not able to log in. After a look at some support websites, one said that occasionally some of Mojang's servers are down, and they are not able to retrieve some user data, and that waiting a couple of hours should fix the problem. Long story short: it didn't.
To explain the issue i have in detail, i willbe using example, hypothetical emails and passwords (for obvious security reasons)
When i first got my Minecraft account (about 6 or 7 years ago), my Dad wanted to monitor my account by using his email and password:
And that worked fine. Now every time minecraft randomly decided to ask for login details I could provide them, and this worked every time untill yesterday.
Once again minecraft decided to YEET on me and request login info, and i filled in the same stuff as i always would, and it did log me in, but only let me play the demo version. I logged in to minecraft.net and it said that my account 'does not own a copy of minecraft'
Insert let me in meme here
I tried logging in to Minecraft few times, before asking my dad to try his password with his email, and came up with the message "Login failed, invalid username and password".
When i clicked 'Forgot your password?' and entered my dads email, and after that mine, neither of us recieved password resetting emails.
So currently im stuck at the login screen of Minecraft launcher, unless I fancy a game of Minecraft demo edition that only lets you have one world, stuck in default survival with no cheats, that will get deleted in 5 Minecraft days anyway; not that that isn't fun
I haven't experienced this before myself but if you log onto your Minecraft account on Mojang.com (same credentials as ur mc account) and go to profile it should tell you wether you own mc or not. If it tells you that you don't, I would suggest contacting Minecraft support (most likely located at Minecraft.net) and ask them for assistance