My 5-year-old daughter caught us having sex. Since then, I have somehow become very paranoid in having sex out of the fear that she will see us again. How do I get this out of my head?

I believe you are suffering from guilt and embarrassment and hence unable to enjoy the act. Don't worry. Be careful from now on. Make sure that your daughter has slept in her room and bolt the door of your room. Enjoy your time with your partner!