How do I get out out of starvation mode?

I didn't mean to go under starvation mode but I really wanted to lose weight. Its not that serious though I've been exercising for about a month and dieting. After the first week I decided to "crank it up" to lose weight faster and it worked the first week and I lost six pounds but now I'm stuck at 158, and I mean that my weight is fluctuating. Yesterday, I weighed 152 in the morning and 154 in the afternoon and back to 158 when i went to sleep. I keep my calorie intake below 1000, but on most days its been between 900-800 calories. Now I've notice I only eat half my meals, I just get full and cant go on. I guess I wasnt noticing and been pushing myself too much because I been having exercise fatigue but still continue. I've been burning 2500-3000 in a day. Please help!