Expected my period on 2 april but it came on 31 march. my problem is the colour was dark brown n was very little in quantity and lasted for 4 days.

Normal Period: This may all be normal. That is unless you had unprotected sexual intercourse. If you did you may want to just check with a home pregnancy test.

Rule out pregnancy: If pregnancy is possible check that first and re-check in week if negative. If not it is an abnormal period but not serious. The dark color comes from the blood being retained for a while in the uterus before being shed.