That's a very good question!
You definitely want to keep SOME calories going into your system. You're very wise about that. Some people who diet think "Oh I'll go for zero calories and zero carbs! That must be best!" Then their body starts to shut down and conserve fat

So you definitely want your body to feel healthy.
Always make sure you eat a balanced set of items in a day - some veggies, some proteins, some fats, lots of water. Take your vitamins. If you do that, then generally you will be OK. If your body is getting a healthy variety it tends to feel safe. If you are eating small regular meals and not feeling hungry then that is key - your body doesn't feel hungry, it feels content.
Yes in a few rare cases someone can do all those things but still somehow be so incredibly low calorie / carb just by what they are eating that they stall on weight loss. If that happens for more than 2 weeks then yes I would switch to higher calorie items temporarily (not HUGELY higher just SLIGHTLY higher) to kick your body back into gear. Also I would ramp up a bit on your activities - go for a 20 minute walk rather than a 15 minute walk. Even tiny changes can really help!