A warm and loving welcome to you!
As Quirky mentioned, you're not a bad mum just a stressed one and understandably so. Guidance, for yourself, is a good idea. Seeing that we're typically not trained in childhood to deal with certain pressures that may come later in life (such as those present in mental health issues or motherhood), it pays to gain support, guidance and skills when those pressures arise. When you consider it, you're trying to cope with certain mental health challenges that are covered in a university education (psychiatry, psychology etc).
As a wife and mum to 2 teenagers, I'm prone to the occasional 'break-down'. They are all beautiful souls, my bunch, but I find that about once every few years I am 'breaking it down' for them, how their behaviour is impacting me. These are pressure cooker events. You can feel the pressure building up and up until someone says something that triggers the release valve and then BAM, you find yourself letting off steam, sometimes severely scolding those around you. It can't hurt to tend to their wounds with words such as 'I love you deeply but I do not love your behaviour. Your behaviour challenges me and we need to work on how to address the challenges we're both facing here'. Such words are not enabling the behaviours (mine included), just addressing them.
SLH123, I believe we humans are designed to let off steam. It's well noted that mental dis-ease (unease) can lead to physical dis-ease. This is the way we tick. Letting off steam ensures that the physical aspect of self is not heavily impacted. Actually, certain health cover businesses will offer discounts to those who are proven to regularly practice meditation (a form of personal mind control). They recognise the link between mind and body.
I find that sometimes family life can heavily impact my identity (my 'I AM'), especially when it's the one thing I'm mainly identifying with. Eg: I AM frustrated. I AM angry. I AM hopeless and so on. Having a positive release valve in life allows me to shift my focus to a more positive identity, whilst taking care of the stress levels. Something as simple as bike riding with my son along bike paths in nature based environments sees me shift my energy and identity; I AM a proactive mum. I AM connected to life/people and nature (spiritual aspect). It becomes a mind/body/spirit well-being form of exercise.
Shifting incredible energy/pressure more toward cooking up 'food for the soul' can be a challenge.