I have used my freshwater tank and my city water inlet for water and I get great pressure from my kitchen sink, outside shower and inside shower however I get very little pressure out of my bathroom sink. There is a switch on the bathroom sink that says pump and I have pushed it but that does no good. Any suggestions on what is wrong with the bathroom sink?

Try cleaning the screen at the end of the faucet. Stuff gets clogged in the little holes and will cut back the pressure. This is usually the cause since pressure is good at other faucet/showerhead. Also you may need to remove each faucet handle, valves and clean the inlets to make sure nothing is blocking the passage through the valves. Last resort look for kinked lines leading to the faucet.