should i be concerned?

awhile ago i took plan b, a week later what i belive to be my period came 2 weeks early. for 9 days it was pretty light and barely there but a had some cramping and headaches for 4 days, today is day 10 and im not sure if this is like a second period or what because it was starting to go away and then bam now its a crime scene, im continuously changing pads and filling them up with blood and that stuff that ive heard some people talk about as like blood clots and im not sure if i should be worried or not im freaking out because my periods are normally 4-6 days and i dont know what to do, is this normal? and should i be doing anything so my body gets back to normal after taking the plan b?