Hi,
Welcome to ehealthforum,
Shorter and lighter periods, prolonged spotting/brown discharge could indicate pregnancy possibility (especially if you are not on birth control measures and have been sexually active without protection during your fertile days/ovulation time). The exact cause can only be made out after careful evaluation. 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). If pregnancy gets ruled out, further evaluation would be done to look for the underlying cause for your symptoms and altered periods/vaginal discharge. Treatment as appropriate (based on examination findings and investigations results) would be started to help you control the symptoms and regulate your periods. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Take adequate rest. Drink plenty of water. Maintain healthy diet.
Take care.