How Long Does Plan B Stay in Your Blood?

Im 16 and I took a Plan B pill in April and i was wondering if it is still possible to detect it in a blood test. Im suppose to take an annual blood test in May, but ive been holding off the blood test because im afraid it might show up in my test results. I honestly regret having unprotected sex and learned my lesson. My parents dont know about me being sexually active and I dont want them to find out. So will it show? Or is Plan B completely gone & out of my system?