Water pressure issue

I have a ongoing issue with my water pressure. I have a well. When we do something that uses a lot of water (like using the washer) we lose water pressure to the whole house. If I run the spicket outside we will get some pressure back but then it will go away at times. We had full pressure back at one point but when we did some wash it went back down. What's confusing is the spicket has full pressure and so does the hose hook ups on the house.

We checked the water pressure tank by letting some air out and seeing if any water came out and none came out. The pressure gauge says we are getting 40 psi

Any ideas?

Thank you for reading!

If you have galvanized pipe system there might be a pipe or fitting that has choked off the flow.
Or you have a gate vale that might be broken and only partially opened.

I often see nipple on water heaters choke up with rust scale from electrolysis.
That is easier to evaluate because it only effects all the fixtures in the house on the hot side.

Look for a gate valve between the good flow and the problem area. If the valve stem just turns and turns then the stem is broken in the closed position most likely.

You don't have any of those in line "Whole house filters" do you?

Does the pump keep up with demand or does the pressure on the gauge go down while your losing pressure at the washer?

As you may already know the flow and pressure available at any point in the system is based on the capabilities of the water source(in your case a pump) and the pressure losses through the piping system.
Without getting into a lot of detail, as your flow demand goes up your pressure losses increases due to increased friction through the piping system and the fact the pump(assuming it's a centrifugal pump) is only capable of a certain pressure at a certain flow.
If your pump is only capable of 40 psi at static (no flow) conditions, you could easily lose a lot of that pressure based on your flow demands and pressure losses through the piping system.
Is this something that was once much better and is now getting worse, which could be caused by one or more of the above suggestions, or was it always relative poor pressure.
To analyze it properly, it should be looked as a system. That is, getting the actual pumps performance curves. That's a curve that shows it's capacity at a specific pressure. Then plotting the piping systems lengths and sizing to the various demands to determine the pressure losses at the various flows. Of course the flows would be limited to the pumps capabilities at a particular flow vs pressure.
It my sound confusing but it's quite simple to estimate what to expect for flow vs pressure at any point in the system once plotted out with all the pipe sizes and lengths, bends, valves and any other device that would contribute to pressure loss and match that against the capabilities of the pump.