My girlfriend and I had unprotected sex and took plan b then put the condom on backwards?

No. I dont think there is a huge possibility for pregnancy when you put the condom on inside out. It probably would have been best to use a different condom but I dont think the risk is high enough to warrant Plan b again. You should always, always use spermicidal jelly or foam when using condoms. This helps to kill any wayward sperm that may have escaped a condom with slippage or breakage (or in the event that you put it on inside out first) Using a condom without using spermicide as well doesnt offer nearly enough protection. It sounds to me like you two are fairly sexually active and in this case, Plan b isnt a good idea. It is not birth control. It is not nearly as effective as birth control plus it is very expensive for the little protection that it offers. Plan b still leaves up to a 20% chance for pregnancy (which is not much better than hoping and praying) Plan b is designed to delay ovulation. If she has already ovulated, it doesnt do anything. So Plan b isnt the panacea everyone seems to think it is If you are going to have sex, your girl needs to be on a reliable form of birth control. The birth control pill (or "the Pill") is one of the most reliable. When used perfectly it is 99.9% effective!! There are other hormonal methods just as safe. Methods like Depo-Provera (the shot) Ortho Evra (the Patch) Nuva Ring, Implanon/Nexplanon (implants into the arm that secrete hormones and work for 3-5 years depending on which you use) as well as Mirena and Paragaurd (IUDs that can work for 5-10 years depending on which is chosen) and these methods are more convenient for some women that dont want to remember a Pill each day! The best thing you could do is to accompany your girl to the clinic or her gynecologist and get her on the Pill or other hormonal birth control! Then you wont have to worry.