Hello, First of all, you do a blood test for beta hcg & USG lower abdomen to exclude intrauterine pregnancy as brown discharge with late period may indicate implantation bleeding. In exclusion of pregnancy, other reasons are hormonal imbalance, stress/ anxiety, thyroid problem, wt gain/extreme loss, irregular eating habits etc. Vaginal infection is also to be ruled out. Do some investigations to rule out underlying pathology like Thyroid profile & other hormone assay etc. One vaginal swab test & urine examination are required. So consult with your doctor and take suggestive measures. Avoid stress, take healthy diet with folic acid & vitamin supplements, control body wt and maintain genital hygiene properly. To get relief from abdominal cramp, you may take some anti spasmodic medication. If you need further consultation with me, then you can visit http://www.healthcaremagic.com/doctors/dr-soumen-patra/63326. Take care yourself.