I want to start by saying my DD is the funniest, cutest little girl and I love her dearly, HOWEVER I am currently on maternity leave with DS of 4 months and really struggling with DD's behaviour.
I just want to add as well that she has always been an incredibly outgoing child well before DS arrived and she adores him (part of the problem is her being determined to cuddle him to death). When the other little girls are sat colouring or playing nicely at playgroups my DD is literally running rings around them and refuses to join in (I have anxiety so this makes me panic somewhat as some of the mums give that disapproving look) anyways...
I am quick to temper, I know this. My maternal streak is limited somewhat but I am aware of this and try to do my best but at the moment I just feel like I spend all day shouting at DD and it's making me feel like a really horrible mother. When she's messing with things/breaking things I'm often trapped under DS breastfeeding and it just makes me want to cry with frustration. I've tried distracting her by asking her to 'make me a cup of tea please' for example which only sometimes works, when it doesn't I end up shouting which is also futile and quite frankly feels toxic.
She's also hitting me and having some epic meltdowns if things don't go her way which I think is normal for her age??
Her little brother is exhausted as he never gets to sleep in the day. She runs over and screams at him to wake up
I can spend ages trying to get him to sleep and then she'll do that and I'll just burst into tears. I'm so tired from sleepless nights so that isn't helping.
I'm actually starting to dread when OH goes to work in the mornings and find myself counting down the hours to when he's home. DS is an angel but doesn't like to be put down and left or will scream (don't blame him!). I'm at the end of my tether 
Desperate for advice! Thanks.