Anger/Depression/Postpartum Blues

Have been feeling emotionally unstable, currently 4 month postpartum. At times i will tend to raise my voice to either the toddler or newborn cause i feel like theres too much to handle? Am i worst mom or isit normal? Im all alone, no maid no parents or in laws staying with me. Is it normal too that you cant keep up with daily activites of your children when you dealing the house on your own? Or you house in a mess when you spent too much time with your children, is this normal or am i just a lazy mom?