Why is my voltage so low?
You'll want to start by contacting your service provider, and asking them if there is a problem with their distribution system. Ask if they're providing poor service due to high demand. If they're not aware of any problems in your area, you should ask them if they can come out and verify you have a good hookup.  If everything with the electric company checks out, you'll want to have a licensed Electrician come have a look inside your home.