No weight gain ?

Hello fellow mummies. I’m week 17 today and I have very tiny baby bump, which looks more like a bloated tummy than a baby bump. Also i haven’t gained any weight yet. Is this normal ? I know that smaller baby bump or no bump at this stage is normal but not gaining weight is normal too in 2nd trimester? My week 16 doc visit, all was good with baby. Now next appointment is at week 21, for anatomy ultrasound. I have always been a slim person. I am 153cm tall, and weighed 45kgs 4 years ago when i got married. Now i’m 48kgs for almost 2 years. I didn’t have that bad nausea in 1st trimester. It was bearable. And now I am also eating constantly in my 2nd trimester, so it’s not that I’m starving myself. Please advise or share your experience.