Question: I feel like there is not enough tension in my novel. Looking at my antagonist, I feel that he is not causing things to get worse and worse, rather waiting and watching. How can I fix this problem and raise the stakes?Answer:
It's certainly true that you can't make life easy for your main character. The events leading up to the climax should make the situation increasingly worse.
Of course, there are different kinds of problems and obstacles you can throw in your main character's path. Some are external, such as plans that go awry, unexpected difficulties, conflict with other characters who have competing goals etc. If your antagonist is not actively working to prevent the Story Goal, you can have a Contagonist to cause delays or introduce temptations that sidetrack the characters.
Other problems are internal, such as the main character's doubts and fears (which can also grow in response to the situation). Then there is the pressure to change, which the impact character can put on the main character.
A third source of pressure is the Forewarnings - signs that the Consequence is getting closer and may occur before the Story Goal can be achieved. You can make these as big as you like. Sometimes, the main character may be unaware of these, but if the reader see them, they add to the tension.
Also, the reader should have the feeling that the characters are either running out of options or running out of time. Make it clear that there are only a few possibilities or a small amount of time to achieve the goal, so the reader can tick them off or count down the minutes.