One good book: The Truth About Women's Hair Loss. I forget the author's name. EXCELLENT reference and very easy to understand.
A few common causes:
1. Post birth symptoms
2. Poor nutrition and increased stress
3. Hormone imbalance/issue
If you are concerned, I would go to see an endocronologist(sp) - hormone doctor. It could just be post-natal effects... just stronger... or it could be a symptom of a hormonal imbalance/issue that needs attention. I had some significant hairloss in my 20s... I used Nioxin, Rogaine and saw the endocronologist.... once I transitioned to a different project at work, it improved 100%... I am now mid-30s and I still have hair:-) It was all stress and nutrition related. I was traveling non stop, drinking way too much coffee and not eating properly/heathly... I was challenged at work and having fun, but way too busy. I was eating very little fish, healthy meat, fresh vegetables, etc... only on weekends when my schedule lightened up. If your hormone tests are all fine, I would take a look at your very hectic yet fun home life, your own habits and see if you can get some more "me" time. Maybe a relative or friend could come once a week to clean or make a home-cooked meal, or you could hire someone part-time to give you a break.
Continue to have a great time and please take care of yourself.