My voice is is cracking and changing? I am a woman, why would yhis happen?

Vocal cords. Usually in women this is due to inflammation on the vocal cords. Although often this is due to something as simple as post nasal drip or even reflux, it is probably worth seeing an ENT doctor for a look down the throat at the vocal cords!
Voice Cracking. Alterations in voice are due to changes in anatomy or altered use of the voice. Sudden vocal strain, reflux of stomach acid, an underactive may all contribute. Allergies and irritants may worsen vocal function. Any alteration in voice that lasts longer than four weeks, see an ear nose and throat doctor to examine your voice.
Lamp or wire? It's right to look at the vocal cords to see if they come together ad vibrate when you speak, but also to see if both of them work in tandem. One of the wires (recurrent laryngeal nerve) leaves the brain, follows the blood vessels into the chest, and makes a u-turn at the aorta to return. A tumor in the chest or aneurysm could also cause hoarseness!