So marijuana stays in the blood for 4 to 7 days for occasional use and i have a blood test today?

so i looked it up that marijuana stays in the blood for occasional use for like 4 to 7 days and i got high 8 days ago at my friends and it was the first time after a month or two so will my drug test be clean or no cuz i heard people naturally already have THC in them so how do doctors tell if you actually smoked or not? so no rude answers please or ill report you cuz i really am scared.and i just want help