When should a lack of weight gain cause concern during pregnancy? How much had you gained by 28-29 weeks?

How much weight had you gained by 28-29 weeks? I lost a pretty decent amount of weight in my 1st trimester then lost about 10 more lbs in the 2nd trimester. In total I’ve lost 25lbs so far. I have steady lost weight at all my appointments. My doctor brought it up at my last 2 visits and asked if I was doing anything to lose weight or if I was making sure I was eating enough etc. which I am I eat a LOT. I have a big appetite and have had no morning sickness with this pregnancy whatsoever, I’ve never thrown up or anything so idk why Ive lost so much weight. With my last pregnancy by this point I had gained back all the weight I lost in the beginning plus 14lbs more on top of that. I am 28 weeks and still haven’t gained back even 1lb. My doctor is going to do a growth scan on the baby next week to make check her size and make sure she’s as big as she should be, but I’m kinda worried she’s going to measure behind since I’m still losing weight. Did this happen to anyone else and was their baby okay or did they measure on track?