MacBook Pro type two spaces automatically

Almost every time when I press the space, my MacBook pro will type 2 spaces rather than one automatically, which causes a huge problem for writing documents and coding.

1. when it recognizes I finish a word, it will add a space after the word automatically.
2. when I hit the space, sometimes it will type two spaces.
3. occasionally the computer will type two letters when I hit other keys.
4. I reduced the sensitivity of my keyboard in setting, but it doesn't help.

Is there a way to stop it?