Hmm ... irritated and erratic - I have moments where I'm definitely irritated (when I was working full time and also home with the kids) but it's not the norm - those are when I need a mom moment to myself, or it's a sign I need some fun for just me.
If you're like that a lot of the time, then you are stressed. That means you have to change up your lifestyle and work/life balance (you may have to drop some things, prioritize and put yourself on the list of things that need attention) - you may need to see a doctor or a counsellor (are you anxious?) - or if you find you are just fatigued and need a break, that too could be that you are worn out. I guess why are you irritated all the time - list it out, and then change those things. That's what I would do.
I agree with the moms below. I have to have time for myself. Otherwise I am super cranky. I exercise - I have a group I train with - I go for walks daily, I have a machine I work out on at home. That's huge - it gives me a boost and is making me healthy. I do very shorts bursts of exercise - it is totally manageable. If I can do it, any one can. My walk is short but clears my head and I am present - I focus on my walk and surroundings. That's huge.
I found when I had kids I let go of my social life for a while - or it was my work friends. Now I am back to having my own friends. We schedule couple time, friend time, etc. back into our lives. That helps tremendously.
I have friends and one sister who always seem on the verge of cracking - stressed and are always 'busy'. They tell me what they have done that day, what hasn't gotten done, and just seem frazzled. I would chop off about 1/2 to 2/3 off their lists, and my family would still function just fine. I think some moms feel they have to do it all. They burn out. Accepting we're not perfect, and not super moms is huge. My house is not sparkling. My meals are basic. My kids go off for the day clean and with lunches though. My house is run like an assembly line. Find a system that works for you. Hard when you have two separate age groups. There is a big age span between my first and youngest so I get it. It will get easier. Good luck :) keep us posted.