Since you just had a baby, it's possible you're having some thyroid problems. About 10% of women have thyroid problems, and most of those happen after pregnancy. For some reason, the thyroid often can't recover from pregnancy and ends up making too much hormone (hyperthryoid) or not enough (hypothyroid). If you are tired, then it's possible your hypothyroid. Other common symptoms are feeling cold, and gaining weight or not losing weight. You can google some of the more uncommon ones. If any of them apply to you, then you see your doctor and have a full thyroid screen done (not just your TSH level checked).