It could be that once you had started eating healthier carbs, your blood sugar stabilised and is now able to maintain itself with a little help from you. It sounds like you're getting all the sugars that you need (natural ones instead of the processed, refined ones in white bread, sugar, flour).
Getting nausea when you're hungry usually means that your blood sugar is too low; I get very irritable, concentration problems, headaches and nausea when mine is too low. For me, it happens most often in the middle of the night (try forcing yourself to eat jam and bread at 3am, followed by a Cherry Coke or Dr Pepper- ugh
).
If you've stopped eating refined and processed carbs, good for you!! If you've lost 20 pounds because of it, even better! Go with whatever has been working for you.