Why does minecraft say that i haven't bought it?

I have bought minecraft and played it for a while. But one day I wanted to change my skin so I went to minecraft.net and tried to sign in but it said my password was wrong so I changed it and I could sign in again but now it says that I haven't bought the game. I was going to try to sign out of the launcher and sign back in but I didn't even want to try that because I might lose my account forever. I already emailed mojang but they haven't answered back. Any body have any answeres?