The best recommendation I can make is that you first determine that your thyroid is functioning properly and that some other medical condition like the post-pregnancy state is not causing the problem. If all is normal, then I would reevaluate the mineral and vitamin content in your diet and, if it seems that diet alone won't give you what you need, a good multivitamin with iron and zinc in it may replace what your body needs to grow a healthy head of hair.
Hair that falls out in patches is called alopecia areata and is an auto-immune condition that needs medical attention. Both men and women can develop some form of male-pattern baldness if it runs in the family. Women do not have such a noticeable condition but can lose hair around the crown of the head or around the temples as a result of a parent or grandparent having the same condition
C. Traxler , MD