Hormonal imbalance, birth control pills, impending
menstruation (PMS) can also cause your breasts to be
swollen or tender.
Fatigue/Tiredness:
Feeling fatigued or more tired is a pregnancy symptom which can also start as early as the first week after conception.
Other Explanations: Stress, exhaustion, depression, common cold or flu, or other illnesses can also leave you feeling tired or fatigued.