1. Sometimes the shut off valves are not opened all the way and that can cause low water pressure throughout your home. Before calling your local plumber, you should check all the shut offs in your house to make sure they are completely open.
3. Your pipe might be clogged. Have your local professional come out and send a camera down your pipe lines. From there, they will be able to tell if it is or not and can clear it out using a Rigid FlexShaft.
2. Overtime, your whole system can start corroding and rupture. If that is the case, you can have the section where the rupture is replaced, but if you do not replace the entire pipe system then ruptures will keep happening and you will end up spending more money in the long run.