Carrying twins and not gaining weight

I'm a bigger person anyways. Before I got pregnant i was 197. However, I went up to 205 then back down to 192, it's been 7 weeks since I've thrown up or been sick, and I'm only 190. Now I'm 16+5 and completely worried about my dr appointment next week. Babies are healthy, which I know is all that matters. He seemed concerned last month, kinda worried about this month :/ with my previous single pregnancies I gained 50 lbs. kinda weird I'm carrying two and not so much now