And don't use the in-store bp monitors as your primary measuring tool!
Use an at home monitor (not the wrist kind either). Make sure you've been fairly resting for about 10 minutes and then take it. The key is to take averages over a period of time.
But yeah if your upper (systolic) is consistently above 135 it's time for a discussion with your doctor. 145 isn't a crisis, but you do need to talk with your doctor on how to reduce it. Diet and exercise come first. Try that for a while to see if that normalizes things.
Check back here for advice on what to do if you hit the "I need medication" stage. We have lots of advice on how to deal with over-zealous doctors.