It could be a normal amount of weight gain for your pregnancy (extra blood, fluid, water retention, placenta) etc, or it could be weight gain from gaining fat. It's probably somewhere in the middle of the two.
Going forward if your nausea is at bay, you could try gently monitoring your diet, lowering your carbs again if that what works for you. You can safely lose a bit of weight in pregnancy as long as you are getting sufficient nutrients and calories in.
I have gestational diabetes, so had to overhaul my diet. I'm 36 weeks and only 5lbs heavier than pregnancy booking in weight, baby is healthy and very long. So I'm not saying that to brag about my lack of weight gain as if it wasn't for gestational diabetes I really doubt this would be the case 😂 but just to show babies can still thrive if the mother is losing weight.
But, this is only if it sits comfortably with you, if your current diet feels right, and making changes right now feels like it'll be too tough on your body then you can also just accept you, like majority of women will end pregnancy holding a bit more weight, but, since you've lost weight before, you can do it again once baby and post partum period are over.