I'm a woman on accutane. had sex and condom broke but also taking bc pills. chances of pregnancy?? should i take plan b as a backup?

Very unlikely: If you have been taking birth control pills at least for a couple of month as instructed then you should be safe from pregnancy. Because of birth defects with Accutane it is mandatory that you take birth control. All the best.

Yes- you're at risk: BC pills being taken at the same time can certainly give you 1 level of protection but having vaginal sex with a fertile male ALWAYS runs you the risk of pregnancy. If you're within 24 hrs. of when you had relations then, Plan B can still work. Greater than that then, it may not be worth doing.