35 yo wife has pain below sternum this pain waxes and wanes over past few days?

Below sternum pain. Pain below the sternum as described may be esophageal in nature, & possibly related to spasms of the esophagus muscle. Less likely but certainly concerning would be heart pain--this must be evaluated asap please. Once she is reassured her heart is fine, other considerations then include: esophageal inflammation, mediastinitis, lung & brochial problems, syndrome x, breast disease. Get it checked.
See doc right away. She needs to see her doctor right away. Even though heart problems are less likely at this age she may be still at risk based upon risk factors. Also she may have other things such as an ulcer . Better safe than sorry!