My advice, which is the same my GP gave me, is to purchase one of these and take your own BP readings, twice a day. Note them in a diary and at the end of 7 days you can calculate the average BP reading. I have been doing this for years now, nailit. My GP relies upon my submitting the details to him especially through lockdowns. It helps him to review my list of medication by telephone consultation!
I know the initial cost may be difficult but this model may be available elsewhere at a lower price or you could take advantage of paying by installments.
https://lloydspharmacy.com/products/omron-m3-upper-arm-blood-pressure-monitor?gclid=CjwKCAjwlqOXBhBqEiwA-hhitNlPcoC7J5GRnLeMUe-8KEDd5DRIUELDBA4jiFB8x84zxyfxgY0rVhoCRlEQAvD_BwE&gclsrc=aw.ds
Don't come back to me and ask why you should have to cover this expense. It is merely my advice which you can take or leave, as you please. I would just add that high BP is a silent killer.
Hope things improve for you.