Is this PPD?

My daughter is 3 weeks old. And I have a 22 month old. Lately I’ve been feeling very sad I guess or angry. I’ve always been very patient with my toddler and lately I just yell at her or spank her when she doesn’t listen without being patient. I feel like a horrible mom. Today I raised my voice to my newborn because she hasn’t stopped screaming then I felt bad. I have no help. My husband is in the military so he leaves early morning and doesn’t return until evening and no family available. I don’t want to hurt myself or my children but I do feel like I’m a bad mom right now and it makes me so upset and disappointed in myself. I love my kids so much and feel horrible for treating them this way.