It's my move. All I have is a king. The opponent has a rook and a queen. I can't move without going into check. Is this a draw?
That's the definition of a "stalemate", which is a draw, i.e. if it's your turn to move and your lone king has no legal move. It can also happen in other situations, such as for example if you also have blocked pawns on the board in addition to the king, since you will still have no legal move. This is often the last resort of the novice, the hope that his opponent will let him obtain such a position. If you are the player with the rook and queen, or even just a queen, in such a situation, you must be careful to always leave your opponent's king a space to move to if you don't have an immediate mate to avoid this occurring. Of course, it's much less likely that you can get a stalemate against a more skilled opponent, although some strong players have "swindled" their equally strong opponents out of a win thereby, one famous case being a long-ago game between Grandmasters Larry Evans and Samuel Reshevsky.
Your description of the situation is too incomplete for us to answer.
If your king is not under check where it stands right now, then the situation is called a stalemate. The game is drawn.
If your king is under check where it stands right now, then the situation is called a checkmate. The game is lost for you, won for your opponent.
By the way, the appelation "discovered check" in the question's title is inappropriate here, it means something totally different.