Starting a business and learning the financial side is tough. Never feel embarrassed about asking for help – most successful business owners have had much help along the way, because none of us are experts at everything.
I would recommend subscribing to Xero and starting bank feeds (which means your banking data is fed automatically into the financial system and you can keep on top of cashflow daily)
While your turnover is not huge, perhaps the starter plan would work for you? You can create invoices quickly and you’ll always have a record of everything you’ve put through the business for succession.
Also a good accountant or bookkeeper (check customer reviews) is worth engaging early on. They will help you to ensure you keep the right records and alleviate your stress.