First Few Days

I'm new to MFP and it suggests the 1200 calorie/day plan for me. It's now my fourth day, and I am loving it! I feel less guilty about what I eat and I no longer feel bloated after eating (probably because I cut out sugary snacks!). It was all great until today, when I had trouble waking up and was surprised that I didn't feel hungry for breakfast. Later at work, I started to feel really dizzy and got cold chills. I tried to eat a Cliff Bar, but I just couldn't finish it. The sight of food made me feel sort of sick. I knew something was wrong so I made myself finish my granola bar, but I wonder what is wrong. I've been eating from all the food groups, drinking water, and taking vitamins, so I am puzzled to what this could be. Has anyone else had this problem? Am I maybe just taking in too few calories or is it something that will pass?