The less you eat the less hungry you get . Try to eat something sweet in the AM , High in protein and fat at lunch , and sweet and fat at night.
Don't snack too much as this increses your metabolisim. If you do snack make it very fatty. Avoid foods that are "bad for you" , but don't worry about calories at all.
New moms often lose their appetites, forget to eat, or are stressed constantly , wearing their bodies down. Thyroid problems are not uncommon after having a baby but they are usually hypothyroid. Hyperthyroid has a variety of other symptoms such as dry skin , bulging eyes, brittle hair, palpitations, excessive thirst , menstrual changes , trouble sleeping etc.. If you are experiencing other symptoms aside from weight loss or don't gain any weight in 2 weeks by eating as I described see your doctor immediately. Otherwise just get your annual checkup and try to slow down a bit in the meantime, you're probably burrning through your calories and then some !
Good luck and let us know how it goes,
J.