Can the implantation bleeding last for 6 days?

I just had my period, it last for 6 days, today is the 7th days, but im feeling nausea and my breast still sore. I can feel my stomach pinching in but im not sure if im pregnant, because when i check yesterday its still bfn. If i did my calculations right, today i am should be 5 weeks pregnant. Help me should i check a week later?