Premenstrual Dysphoric Disorder (PMDD): Given Shelby's symptoms of sensitive nipples, stomach pains, and lower back pains, which have been persistent for a couple of weeks, along with her history of depression and anxiety, PMDD is a strong consideration. These symptoms align with common premenstrual symptoms, and the impact on her daily life, including panic attacks, further supports this diagnosis.

Irritable Bowel Syndrome (IBS): The stomach pains could be indicative of IBS, especially if they are associated with changes in bowel habits. The lower back pains and sensitive nipples could be unrelated or secondary to the stress and anxiety that often accompany IBS.
Anxiety Disorder: Shelby's history of anxiety, coupled with the current symptoms causing panic attacks, suggests that an anxiety disorder could be a primary or contributing diagnosis. The physical symptoms could be manifestations of her anxiety.
Depression: Given her history of depression, it's possible that Shelby's current symptoms are related to a depressive episode. Physical symptoms like pain can be common in depression.

Pregnancy: Although not immediately apparent, pregnancy could explain the sensitive nipples and potentially some of the other symptoms. Missing a pregnancy diagnosis could have significant implications for Shelby's health and any potential fetus.
Endometriosis: This condition could cause the lower back and stomach pains, especially if they are cyclic. Endometriosis is often missed and can significantly impact quality of life.
Ovarian Cysts: Similar to endometriosis, ovarian cysts could cause pelvic and lower back pain. They are a condition that should not be missed due to potential complications like torsion.

Polycystic Ovary Syndrome (PCOS): While not extremely rare, PCOS could be a consideration if Shelby's symptoms are part of a broader hormonal imbalance. However, a diagnosis of PCOS typically requires more specific criteria, including irregular menstrual cycles and signs of hyperandrogenism.
Adrenal Insufficiency: This is a rare condition that could potentially cause a variety of symptoms including abdominal pain and mood changes. It would be an unusual diagnosis but should be considered if other explanations are ruled out.