Rough morning - how do I regulate myself better?

I was harsh towards my 20 month old and I feel really sad about it.

I didn’t sleep well, the house was a mess, and I’m about a week before my period. I feel like my hormones are going crazy around this time and it fills me with anger. Since having my baby, this irritability/anger before my period has become much worse than it was before pregnancy. Can anyone relate?

Usually I manage to regulate myself, but this morning normal toddler behaviour annoyed me more than it should have and I raised my voice over completely unimportant things. He didn’t deserve it at all 😔

I apologized afterwards and explained that it wasn’t his fault, but I’ve still been feeling bad about it. I don’t get physical and I haven’t yelled until now. But
I know that it will get more challenging and I really want to get better at handling my own emotions. I was in therapy for depression before pregnancy and I’m considering going back.

For those of you who’ve worked on emotional regulation, what actually helped? Books, therapy, podcasts, practical techniques, anything?