is it okay for me to only eat 1000 calories a day?!

I recently started this low calorie diet, where i don't eat over 1000 calories in 1 day and i exercise and burn a little under 700 calories a day, used to weight 320LBS, but now i weight 313 (in a matter of 2 weeks) is it safe for me to keep dong this or should i get more calories in my system, BTW im 18 years old and 5'9, and i need to have a maxium weight of 200LBS by next year may so that i may join the U.S.M.C, so basically is what im doing dangerous or should i keep it up, i have been feeling a little dizzy but nothing i've never had to deal with.