Controls Not Working Correctly

The version of MacOS High Sierra version 10.13.6. The version of the Minecraft I am on is 1.13.2. So what I expected to happen was that when I would want to place a block I would right click it. What actually happen was that when I left clicked I would break the block instead of placing a block. And if I right clicked to break I block it would. But what actually happened was it broke the block as expected.