*Advice* I feel embarrassed and concerned.. I am not showing and not going weight.

I am about to be 19 weeks and I haven't gained any weight and I am not showing what so ever. I was underweight to beginning with however I have tired my best to consume more calories with much difficulty! I feel extremely full and sick after eating the smallest amounts lately. I previously had gastritis from antibotic use that I'm not sure is 100% healed so maybe that has something to do with it too. I am currently trying to eat like 5/6 small servings of food though out the day with vegitarian protein, vegetables, fruit, healthy fats and non daily milk /yogurt. Which I am struggling with hearing shaming comment from many people (strangers, nurses, friends, family especially my husbands family) questioning if I am actually pregnant, or if I am intentionally trying to strive the baby.. I am concerned because I am not showing. I have been able to feel the baby moving. And all of my ultra sounds have been good he is looking healthy and seems quite active. But i always think his home looks small for him on the screen of he doesn't have room. Has this happened to anyone else?