Not sure if this is in the right place and apologies for the lengthy newbie post but am at a complete loss. I don't know what to do. I have 2 beautiful girls who (despite what I say) I love dearly. My issue is me. I cannot be nice to them. All I seem to do is rant and rave. The eldest (6) bears the brunt as in my deluded mind the 3 year old can do no wrong. She does a lot wrong in fact, but the eldest gets the raw end of the deal as I suppose I think she should know better.
The 6 year old is actually quite nice! But I can't be affectionate with her, I don't like her near me. I flinch when she tries. This partly stems from her having rumination syndrome, she is effortlessly sick (regurgitates) but keeps it in her mouth, rechews and swallows again. This makes me heave.
She is also super clever and picks up on these things which is heart breaking for me. I'm sure they're both scared of me, I admit, I have smacked them. I really dislike the person/mother I am becoming. I get wound up far too quickly and what was probably a minuscule hiccup in the day I can turn in to WW3 in an instant!
Thanks for reading..... 
Basically, what I am after are any suggestions for calming me down, snapping out of this mood, ways to discipline her (6 year old) without mindless yelling at her. She starts smirking when I tell her off which sends me into a blind rage and it frightens us all 