High blood pressure

So I went to my 20 weeks anatomy scan and everything was fine with baby . 2 weeks ago my doctor

Prescribed me to start taking baby aspirin because my readings were high the last 2 appointments. So at this appointment the MA did my reading and it was 170/60 and then she took it again right away and it was 120/60 .

I am confused on how it dropped back to normal

Right when she took it again . My doctor she just told me to monitor myself at home so I bought me

Some blood pressure cuffs off Amazon last night . Should I be more concerned or was this a error on the machine part . I was hoping that this baby aspirin is working . I don’t want anything to happen to my

Baby either because I have made it this far and I don’t have any swelling any nausea or blurry vision .