If you've asked how to track monthly expenses, you've probably already tried once and stopped — that's normal, most people do, and it's rarely because they didn't care enough. It's data entry. Sitting down to type in three weeks of coffees and petrol and Amazon orders from memory (or worse, from a pile of receipts) is tedious enough that "I'll catch up later" turns into "never". The habit dies at the typing stage, not at the caring stage.
The fix isn't more discipline, it's less typing: start with one week, not the whole month, and log expenses as they happen rather than trying to reconstruct them later — or import a statement you already have and let it do the sorting for you. Either way you get the same result without the dread of a backlog. This tracker does both (manual entry for the day-to-day, statement import for catching up in one go), with no bank login and nothing to sign up for. Just track one week and see if the pattern in it matches what you assumed.