flava - are you ovulating? pH of 4.8 is totally normal if you are not ovulating, that's the natural pH of the vagina. It's the CM that raises pH so if you have very little CM to test, your pH will seem really low.
Take some Robitussin and see what happens - you will make some more CM to test and it will probably be higher in pH.
Don't worry, we will get that pH up.