Is there a way to view all my computer history? I want to find out if my spouse is watching porn.

Yeah check the history though any guy who is watching porn and not letting his wife know is probably wiping his traces (virtual and physical) clean so you might end up with nothing. If you have serious doubt confront him or you could install a spy monitoring software to check out what goes on the PC. But take care once you walk down the road of distrust its a long way back especially if both arent ready to forgive.
Another question you need to consider if he is watching it what are you going to do?

Why don't you just ask, instead of looking at the history?

If you have safari then you go to the google box and type in any letter and look to the bottom

Tell me what your running...Internet Explorer, google chrome, Firefox?

Click the arrow from where you type a website? And I agree with jack just ask

Computers always leave traces of everywhere you go, but the only way I can think of is to take it to the authorities to get it checked >.> other than that I don't know.