Not gained any lbs💪

I am already 17 weeks & 1 day pregnant & i haven't gained 1 lb at all.. My belly is growing & this is my 2nd pregnancy but ever since i got pregnant I've just been losing weight.. Now im staying the same but the doctor doesn't have any worries or concern yet.. My doctor is just worried that i will get preeclampsia so i am taking asprin everyday with my prenatal!! I eat like crazy as well & drink plenty of water! Has anybody experienced this or is also experiencing this as well??