I have the marina. regular periods every month. this time two weeks after period i've had dark brown to nearly black discharge for 3 days now ?

Most likely normal.: The dark brown/black discharge is most likely 'old' residual blood from your vagina. You may have had some spotting and the blood stayed in your vagina for a while. When this happens, the blood looses it's oxygen content and appears dark brown/black. If there is no odor to the discharge then this appears normal. If there is an odor you may have an bacterial infection (bacterial vaginitis).