Pregnancy weight gain mystery

I’m 5’5” and was around 128–131 lbs pre-pregnancy. I’m now about 170 lbs with ~8 weeks to go, so I’ve definitely exceeded the recommended weight gain for my starting BMI (recommended 25-35lb total).
I’m not worried about it, mostly just curious. Looking in the mirror, I really don’t see where ~40 lbs went. I have a fairly large belly, but baby is average. I don’t have any swelling in my legs, arms, or face either. And I still have 8 weeks to go!
I eat pretty healthy and only organic/clean food: lean meat, eggs, Greek yogurt, fruit/berries, vegetables, etc. Very rarely I eat something unhealthy. I also strength train 3-4x/week (sometimes more) and walk 5-10k+ steps/day.
Has anyone else had this experience? And did you ever figure out what accounted for and contributed to all the extra weight? It feels like a pregnancy mystery to me 😅