I need help, I’m at a loss

First, I’m dealing with PPR.. which isn’t helping any of this

My 3 year old (will be 4 in October) has been throwing the most insane tantrums that give anyone a headache that’s near. She screams if she doesn’t get her way. It’s over anything. If I don’t do/say exactly as she wants, she loses her mind and nothing I do helps de-escalate. I’ve tried everything. Everything. I have to literally walk away and take deep breaths because my PPR makes me want to turn into the hulk. I hate this so much. I love her so much but I am mentally drained from it. I have no idea what else to do and I feel like a complete failure. I have a 4 month old as well who starts screaming too when she is. So then I have two screaming children and nothing I do helps. I cry myself to sleep almost every night because I feel like my 3 year old must hate me or something. I just feel like a failure and I have a never ending headache from all the screaming. I’m trying my best to keep it together but I have lost my cool multiple times. I’ve apologized to her over and over but I feel like she doesn’t understand. She also has a speech delay so that makes it even harder to reason with her and explain to her anything. Please no judgment, I’m honestly doing my best with absolutely no help at all. My husband is thousands of miles away for work. 😭💔