I know this is the basics, but have you first made sure that the main water shut off valve is all the way open? I find many are not, and there is ‘good’ pressure when the faucet is initially turned on, then the pressure dwindles to almost nothing as the flow is restricted at the main water shut off.
Second, is there a hose bibb near you main water shut off which you can check for flow and pressure?
If this is also low, have a licensed and qualified plumber check the pressure at the water meter. If pressure is there, you may have debris blocking the main water shut off valve.
Or, if this an older house with galvanized plumbing lines, the lines may be clogged. If that is the case, it may be time to think about re-plumbing the house.
Have your plumber advise you on your next course of action if you have pressure at the water meter.