Weight for 2nd pregnancy

Alyssa
So for my first pregnancy I was young and only weighed 98 lbs. I was very active and fit , but I ended up being about 163 when I gave birth. Now I'm 5 years older and pregnant again. Starting weight was fluctuations from 112 down to 102 . I have horrible morning sickness but I am not as active or fit as I was the first time. I went down to 98 lbs about 16 weeks and now I'm almost 20 weeks and only 102 lbs. I eat like a pig and try to consume proteins and fats but I'm just not gaining. My doctor hasn't had an issue with it but has commented on how tiny I am. EVERYONE has made the tiny comment. I was just wondering anyone in their mid 20's who had this same issue maybe some pointers ?