I would keep a record of your blood pressure and your symptoms for 2-4 weeks then see a doctor. (Or you could see a doctor first.) On second thought, I'd see a doctor first. Doctors can be weird if they think you are "self-monitoring".

There's something called POTS, which you can have to a greater or lesser degree, and it can cause lots of fatigue and other unpleasant symptoms.

Some people just have low blood pressure and don't notice any symptoms from it. If you're having symptoms, better to see a doctor.