Will the blood tests for roaccutane tell my skin specialist im NOT on the pill?

I went to my skin specialist 2 days ago and got prescribed roaccutane. Because im an 18 year old female, the doctor pretty much insisted I go on the pill also because of the birth defects, I said I would prefer not to (because Ive been on the pill (3 different types) before and experienced weight gain) but he actually wouldnt let me have the roaccutane prescription unless I gave him a note from my GP saying I was on the pill. Went to my GP last night, got the pill script and letter, have to wait a month until I can get the roaccutane script (time for pill to work so im protected from pregnancy). Im getting a blood test tomorrow and another one in about 3 month. Im seriously considering not going on the pill because Im not promiscuous, dont have a bf and can contol myself. my question is, is there anyway my skin spesh will find out im not on the pill? do the blood tests i have to take tell the skin spesh im not on the pill? I dont want to worry him, but im 100% confident in not getting pregnant in the 6 month period ill be on roaccutane. any answers would be great :)