How can I stop undereating?

Five months ago I decided I wanted to lose weight, and generally become healthier and fitter. So far I've lost around 29lbs, however in the last two weeks I can't seem to manage to eat more than 600 calories a day. I know this isn't good, originally I would eat 1200-1500 to lose weight steadily and hit the gym twice a week. In this last two weeks of under eating I've lost 6lbs.. again that can't be doing me any good, but I just can't seem to stomach the food, I try to eat as much as I can but I feel unwell and bloated almost instantly after eating anything. I eat a pretty good diet generally.. complex carbs lean meat etc. Part of me wants to go eat something now to increase my calories for the day but I just don't feel hungry, and if I eat now when I don't feel hungry won't that just mean I'm overeating and will gain weight? HELP!