very light not painful period , 3 days diarrhea?

Hi,
Welcome to ehealthforum,
Absence of usual PMS symptoms, lighter and shorter periods, changes in bowel habits could indicate pregnancy possibility. Look out for development of any other new symptoms if pregnancy is suspected. If you suspect chances of pregnancy, consider visiting your doctor/gynecologist at the earliest for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet.
Take care.