How can I see my game is submitted

Go to your game's page, look at the right corner. If you see a badge with "GMTK Jam submission" written next to it, it's submitted.

What Fupi said works, but you can also see it by clicking on 'Jams', and near the top will be 'Jams you've entered'. The top one will probably be GMTK unless you've signed up for others while GMTK has been going on. In the box, if you have submitted your game, it will say 'your submission: (Your game name here)'.