Even if you weren't using regular hormonal contraception, you cannot get pregnant from sex you had that late in your cycle. Not if your periods are regular each month. It's worth learning how the menstrual cycle works, to save yourself a lot of stress, & to save your body from unnecessary chemicals.
Plan B is a huge dose of artificial hormone for your body to deal with. It's meant for total emergencies. You may experience hormonal symptoms for weeks or months after using Plan B, especially on top of your regular hormonal birth control. Your periods may come at the wrong times until things get back to where they were before Plan B. Just keep taking your regular birth control as if you are bleeding on your placebo pills (assuming you're on a type of pill that has a placebo week), & things will eventually fall back into place.
I also suggest seeking advice from a doctor who deals with complimentary medicine, to ensure that your detox pills aren't making your regular hormonal birth control less effective, if you haven't already. If they are making it less effective, then you may end up pregnant.