Bug in my Mojang account.

I just bought Minecraft Java Edition and then I downloaded the Minecraft launcher, after finish downloading, i login using my Mojang account and it says there is a bug, i log out then log in again and it shows play demo. I tried login back into Minecraft official website using my Mojang account and its completely reset. My username was not the same and my Minecraft java edition was gone. Please help me look into this bug. I wanted to play Minecraft and its very expensive in my country