I had one sitting of bad diarrhea two hours before taking my pill.no diarrhea after that. i took a plan b just incase, do i need protection for 7 days?

Birth control pills: Your regular birth control pills should not be affected by having diarrhea. They work by preventing ovulation so if you are taking them as prescribed, you should be at no increased risk of becoming pregnant (they are not 100% effective so there is always a small risk). Protection with a condom is a good idea for preventing STI's otherwise.

Yes: You need to use protection any time you don't want to be pregnant but your birth control pills should be adequate as long as you take them correctly. Remember to also use condoms to decrease the risk of STDs. Hope this helps.