Are you breastfeeding? If yes, you'll likely have hunger pangs. Even if you're not, this soon after giving birth your body takes a while to get back to normal. Don't beat yourself up. Negative self talk won't make you do better.
Also measuring is so important, and you need to do it. No ifs or buts about it. What you might need to do is plan your meals so you know when to eat what. Make sure you have 5 or more so you don't have a stretch of time where you'll get hungry. Plan your meals and prepare your snacks ahead of time so you don't find yourself to hungry to make your snack and go for something else. And example would be to have an apple, an ounce of cheese and a few almonds measured out and ready to put on a plate together.
If you do slip, don't beat yourself up and don't let it ruin your whole day. Just carry on.