Voice therapy is relative easy to explain but somewhat difficult to do. If our voice is out of the feminine range, we use something called the head voice. It simply means we tense the muscles between our larynx and jaw when we speak and it will rase the pitch quite a bit. You use the same muscles when you swallow and if you put your hand gently on your larynx, you will feel it move up when you do either of these actions.
The head voice is used in singing so a music instructor could show you how to do this or you might find it yourself. To do it, say Aaahhhh in your normal voice then start raising the pitch and tensing the muscles between your jaw and larynx. When you switch to your head voice, there will be a break in your voice. At the age of 14, your voice may not have dropped out of the feminine range but that would take a little testing to determine.
After that it becomes a matter of using the sing song voice that women use instead of the flat voice that men use. If you listen to a woman news reporter, they are often good examples of a feminine sounding voice.