I am 20 years old and possibly could have been pregnant but not sure! I think i am having a miscarriage... i was 2 weeks late for my period but i woke up yesterday and i was very heavily bleeding... when i wiped i had a very large maroon almost dark brown clot come out! I waited to do anything and now today i am having severe abdominal pain, i am having dizzy spells, still heavily bleeding, and hot and cold flashes! Did i have a miscarriage and should i seek medical attention immediately?

Looks like it is a misccariage. You should not have cramps and bleed with chunks when you are pregnant. You will need to get your uterus cleaned well to avoid any complications. Please meet your gyne today itself and get uterus cleaned such that you dont face infertility problems later in life and alos the chances of infection in your uterus will be less if it gets cleaned well.