How do you know if you have PPD

I cant tell if Im just frustrated, maybe overwhelmed? Or if Im depressed… I had a baby 3 months ago. I absolutely love her. I have 3kids under 3 though and Im a SAHM. I love my husband and family very much but some days the little things my husband and I might disagree about send me into a wave of emotions. I just want to cry, I never get alone time, I miss my family who lives far away, I have zero friends close by and Im

just fucking miserable. I get so emotional about things, we took the kids to a parade the other day and I teared up just thinking how happy they were and I was to be out of the house. Tonight my husband insisted I take the newborn with me while I run to the store. I flipped out on him and now I feel like Im going to have a breakdown. I told my husband not to talk to me the rest of the night and I never say things like that to him. But Im so frustrated with never having a break. My best friend lives 8hours away and we talk daily she really helps me stay sane, plus she is a SAHM mom too. I just feel so emotional happy, sad, angry, all the time.