Bought minecraft but now it says I can only play demo?

I bought minecraft a while back (can't recall how long, exactly. Sometime last year at least)
I played it for a while then got super busy with school work and haven't played it for a few months.
Now that school's out, I tried to log back into my account and play ( I never logged out, it automatically logged me out after the extended period of time I guess).

I logged in and went to play, but it says "play demo" instead of "play".
This is the second time this has happened, it happened last year too and I ended up repurchasing the game because I was unable to find my receipt from the first time I bought the game.
Well, go figure, I can't find it this time either in any emails. -.-
I'm still looking, but anyone else that has had this problem and can tell me how to deal with it would be much appreciated. I'm not going to purchase the game again.

This has happened to me on Xbox 360 before. What i did was I signed out in the title screen and signed right back in. Sounds dumb but it worked. It gets annoying but its worth it.

Some one told me to sign in on another computer and then sign in on your computer, I don't know if it will work for you but it did work for him (goes over to my friends computer) if it works visit my channel ZacTCA