Hi OP. sorry you’re going through this. It’s really brave to ask for help. Sounds like you’re already looking at therapy. “The book you wish you’re parents read” is amazing.
So many of us are ill equipped for parenting if we don’t have good role models or support. You aren’t alone in this.
Try to embrace parenting. Acknowledge that it’s your frustration, and baby is not at fault. They are hard work and it can be frustrating.
Have you tried mindfulness? I’m being more ‘in the moment’ and it’s definitely helped. I rarely shout, but I’ve had my moments where I’ve simply been overwhelmed or frustrated. Shouting only brings on mum guilt and will make you feel worse, so definitely curb for your own sanity. Baby will be fine, so try not to worry.
Going forward, think about ways you can make parenting more fun for all of you. Make everything a game. Instead of “silly child” or “naughty baby”, try to sing song things like “what are you up to little squirrel” or something like that. Ignore bad behaviour, keep “no” for dangerous tasks, reward and praise the good. Distract baby when getting them changed. And always remember you can put dc in a cot and walk away for a moment if it’s too much.
Play lots and don’t stress when you’re in the middle of something and have to stop. Unfortunately, babies are very active and time consuming.
It will get better, I promise x