You should feel very proud of yourself for getting out there and back to work. It's not easy. Early days are always tough with finding your feet in a new place and sorting a new routine. Be kind to yourself. If it makes you feel any better, lots of us get the wobbles when we get back to work after a couple of weeks of annual leave (I certainly do!).
Definitely don't leave the job!! Give yourself time to learn the ropes. By then, things should have settled a bit more at home, and I bet you'll be feeling more settled in the job (and more confident!).
I've just changed my shift pattern (still working FT though) as DC2 is now at secondary, and that has taken a bit to get used to. Before, I was working shorter shifts (over more days), but FT hours (so always home to cook supper), now I'm working 7-8, 3 to 4 days a week. No DP/DH, and I'm the breadwinner, so the kids have to get on with it.
What's helped us re: meals...
I've (finally!) sorted out my freezer and pre-cooked/froze a load of pre cooked meals. On days off, I will cook a double portion of a meal and freeze half. On days I work, I take out a frozen meal and when DC (age 17 and 11) get home from school they have to reheat it for themselves at their normal supper time. I eat a bit when I get home later, and there's normally some leftover for lunch the next day. That seems to be working well, and it saves me money and stressing about meals! Might be worth a punt? I'm not sure why your DH isn't taking meal prep on though. It's bloody crap finishing work after a long shift and having to sort out a meal when you're knackered!