Is it ok to watch movies about sex or look at pictures about sex--as long as I don't actually do anything?

Why do you want to do what you suggest? I know that there are times when a picture will come across on the internet or you will see a magazine on a newsstand or you will be watching a movie that has one sexual scene in it, but why do you want to choose to deliberately watch a movie or look at pictures about sex? The answer to that question will tell you why what you envision is wrong. Are you planning to do research for a clinic on sexual practices? What is your rationale? Is it because you get some kind of stimulation that makes you feel good in a sexual way?

Listen to what God says:
Matthew 5:27-28 “You have heard that it was said, ‘Do not commit adultery.’ But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.”
There is such a thing as lust that is sexual. It shows itself in a sense of excitement about a person who is not your spouse that is sexual. That is a sin.

I would encourage you to talk with your pastor about this. He can help you sort through the issues involved in your life much more personally than we can through this medium.

God’s blessings!