When I right and left click, things break

As I have said, I can't seem to place anything in Minecraft which I am playing on a new MacBook Air [so the problem can't be with my laptop]. Whenever I try placing something using my right keypad, it just breaks stuff and when I try placing something with left keypad, it just breaks stuff. I have tried fixing my settings and connecting a mouse but both sides break items! 

What I expected to happen was...:
When I right/left clicked items and blocks would break. When I left/right clicked items and blocks would be placed.

What actually happened was...:
When I right/left clicked items and blocks would break. When I left/right clicked items and blocks would break.