Are there any diagnostic studies that should be ordered on this patient?

A 19-year-old woman presents because her normally regular menstrual period is now 3 weeks overdue. She reports fatigue, bloating, and breast fullness similar to what she normally experiences prior to menses. She began menstruating at age 12 years and, after her first year, the periods have been regular every 28 to 32 days and are associated with mild menstrual pain. Are there any diagnostic studies that should be ordered on this patient? Why? List the primary diagnosis and at least two differential diagnoses for this patient. Explain your reasoning for each. Discuss your management plan for this patient, including patient education, referrals, and follow-ups.