My stool was big and hard very dark colour but when I wiped it and stuff the marks were brown. Was stool just very dark brown? Eaten lots of chocolate

Black, tarry stool? If the stool is black and like hot tar consistency, it's possible that there is blood in the stool. Stool color varies dramatically with what foods you've eaten, dyes that may have been in processed food or in your case maybe even very large quantities of dark chocolate.