I know it's normal to have implantation bleeding up to 2 weeks after ovulation... But I'm 5 weeks and today I've been having a lot of cramping almost like menstrual cramps and started spotting evertime I go to the bathroom today.. Now I'm having some pain in my back.. 1st pregnancy and nervous... Not sure if it's just normal implantation or something I should be worried about.. How long does implantation bleeding last?