hello there is history of tubal ( ? ligation ) done history of previous normal regular periods now history of delayed periods followed by spotting with abdominal cramps ( left side ) if a patient with similar history comes to me I would first suspect ectopic pregnancy if would do her pervaginum examination to see uterine sixes, cervical motion tenderness, any adnexal mass & do her upt if Upt is weakly positive or examination finding suggest ectopic pregnancy i would admit her , do her bhcg & urgent ultrasound to confirm the diagnosis .she may need urgent laparotomy also tubal ligation has a chance of failure & if failure occurs the chances of ectopic pregnancy r high although u have history of hypothyroidism ( not on medicine ) which may also delay periods & although ur last sexual contact was 4 weeks ago still in advise to get upt with first morning urine sample & gynaecological check up with bhcg to rule out ectopic pregnancy if Upt strongly positive u still need ultrasound fetal well being to check fetal viability hope this helps you