The Reluctant Empress - The Empress of Kaydor, #1

Blood Will Tell Ninallia is young--young and desperate. She decides to sell the only thing she owns to save her family: her body.   Believing family stories that they descend from royal blood, she agrees to become a surrogate for an infertile couple.  The lucrative agreement will provide for her family for several years.  Ninallia's world is turned upside down when the Emperor and Empress are assassinated, and she discovers that the child she is carrying is the heir.
 Her life and that of her unborn child are in grave danger.  Disguised as a boy, Ninallia flees.  To survive she must find help. She finds two allies, a League Soldier and a Sister of the Order.  Together they must keep Ninallia alive until her son is born and his blood tested to prove that he is the Imperial Heir.