Well done on deciding to tell your mum.
For some reason I get a sense that your dad may not be of the same mind as pretty much everyone on this thread, apologies if I've got that wrong. I do hope you are able to tell him and that he will be supportive. However, if he is the type of man to, even unintentionally, victim blame somewhat, perhaps suggesting you must have done something to set him off, then please don't listen, you are not to blame for this at all.
If he is not the sort of person who understands that a man does not hit his partner, end of, then your mum may find herself stuck in the middle, wanting to support her daughter but having her ear bent by her husband suggesting you may have created the problem.
Should this happen, and I hope it doesn't, again apologies if I'm completely on the wrong track, don't give up and assume you're in the wrong. You are not. There is no justification for your husband hitting you. Text him to back off and stop communication with you while you consider what to do, mention in the text that you have been hit by him for the last time and you will not allow your children to be exposed to abuse.
Speak to Women's Aid (yes it's that bad, you need to), tell other people, don't be ashamed, read books like "Why does he do that" by Lundy Bancroft, you will see your husband in there. Keep posting here for support, but please don't go back to him.