18 weeks and no weight gain

Justice • son born 12-9-16👦 missed miscarriage 7-12-17 at 10 weeks👼 blighted ovum 2-5-18👼baby girl born 11-25-18👧
Hello ladies. I'm 18 weeks and I have gained no weight whatsoever. In the beginning I had food aversions and i didn't eat too much and lost 10 pounds. As soon as I could eat I gained it back. This was a couple months ago. Now I've been making sure to eat every meal of the day including snacks and I can't gain anything. I'm 148 lbs and 5'1 my normal prepregnancy weight. My little guy is getting stronger because I can feel him on the outside of my stomach now and my belly is getting bigger. I was told I should have gained 10-13 pounds by now and I can't seem to gain 1. I work full time so im on my feet alot. But I've been eating alot more than I usually do. Is this normal or should I be concerned. Idk how my belly can be getting bigger if im not gaining weight. Any advice? Or explanations? I'm starting to worry