First: is it one fixture or all of them?
This single question splits the problem in half. Low pressure at one tap is almost always a blocked aerator, a partly closed angle stop, or a failing cartridge inside that fixture.
Low pressure everywhere in the house means the problem is upstream - at the pressure reducing valve, the main shutoff, the service line, or the pipe itself.
Test the static pressure
A gauge on an outside hose bib costs very little and tells you a lot. Normal residential static pressure sits between 45 and 75 psi.
Below 40 psi with everything closed suggests a supply problem. Above 80 psi is a different problem entirely, and it is the reason a lot of North Carolina homes go through fixtures and water heaters faster than they should.
The four usual causes
A failed pressure reducing valve. These have a service life, and when the internal spring or diaphragm gives out, pressure drops across the house. This is the cheapest of the four to fix.
A partly closed main shutoff. Gate valves seize part-open, especially after years untouched. Worth checking before anything expensive is considered.
Corroded galvanized pipe. Older homes with original galvanized supply lose diameter to internal rust until flow chokes. This is what a repipe solves.
A leak on the service line. A line losing water underground drops pressure and raises the bill at the same time. The meter test confirms it.
The meter test anyone can do
Turn off every fixture in the house, including ice makers and irrigation. Go to the meter and look at the low-flow indicator.
If it is still moving, water is escaping somewhere between the meter and your fixtures. That is a leak, and it needs locating before it undermines a slab or a foundation.