Weight gain or not

I'm 20 weeks I lost 11 pounds my first trimester and I am now halfway done. I haven't gained even a half a pound of the weight back. Anyone have any insight or going through this themselves? I see my doc Monday they haven't seen me in 5 weeks so  gonna ask about it when I'm there. My tummy is growing tho but I feel like I haven't grown in about 2 weeks.