i had a baby 18 months ago and had the contreceptive injection a few weeks after giving birth but only had it once since then ive had no periods and im not pregnate..recently i started bleeding for 5 days it was so heavy i had to wear 3 sanitary towels at the same time and changed them neerly every hour even so it didnt always stop it leaking since then ive been having brown blood every now and again and it lasts around 2 days and small clots of black blood and it smells weird.. is this a sign of something serious?what should i do?