How's your stress level? I know my hair falls out more when I am stressed out -- it's one of the things that I watch for to keep my stress in check. If you are stressed out, then you need to think about what you can do to relieve that stress. Exercise and healthy diet help me, along with some quiet meditation time every day (not easy with 2 kids, but possible!). And, while we hate to admit it, women can be affected by the same genetic traits that make men go bald (although we ususally just end up with thin hair, not baldness). Your son is old enough now that it's not the build up of hair from pregnancy. If you are really worried about it and don't want to take the pill just because they "think" it's hormonal, have them test your hormone levels to find out.
Good luck to you!