Welcome jobrun
Last month it felt like we were constantly going to the shops and we overspent on groceries and this month I've decided once a week and that's it.
If you didn't have the money/access to the shops you'd have to make do so I just enforce that upon myself. Milk and bread freeze and they're the main things we pop to the shops for spending much more while we're there, keeping a stock of it avoids this.
Meal planning is great, reviewing what you've spent in the past couple of months will help if you can, otherwise work out what you can afford to spend and work with that figure, be realistic though.
Write out all known and ad hoc expenses, and occasions like birthdays/christmas/one off bills like insurances, and the unforeseen things like car breakdowns etc
Get your dh on board if you can too
Get your financial house in order before next maternity leave, I didn't do that and my dd will be 6.5 and ds almost 3 before I'm fully sorted again.