Teary, overwhelmed, and strange is normal in the postpartum weeks and, sometimes, months. You may be irritable and sometimes angry. You may have dramatic mood swings. You may shed tears for no reason and find yourself unable to cope with situations you would normally handle with ease. You may blow up in anger when those around you least expect it.
This is normal. It is normal to have an emotional reaction to a major life change — and a new baby is a major life change. It is normal to be stressed by the demands placed on you as a new mother, to be daunted by the responsibility that is suddenly, literally, in your lap. It is normal to be exhausted when your sleep is constantly interrupted. And it is normal to have a host of physical and emotional reactions to the dramatic postpartum change in your hormone levels. The rapid drop in estrogen levels causes hot flashes, depression, and trouble concentrating. (Like you really need a preview of menopause at this point!) The drop in progesterone can cause anxiety (progesterone, in high doses, has sometimes been prescribed to relieve anxiety). The fall in the level of thyroid function can make you feel sluggish. Mood-controlling hormones, such as serotonin and dopamine, drop as well.
For some women, the hormonal changes may be too extreme to handle without a doctor's help and/or medication. Accept the help if you fit into that category. You're not being weak, because being better able to control the hormonal changes will help you be a better mom.