6 weeks Preggo...weight loss

Cami
I used to be into cardio big time but I've slacked off big time and now I don't do much other than walks. What do you reccomend to keep in shape when pregnant. I only want to gain 20-25lbs while pregnant and I'm trying to watch what I eat so i don't turn into a whale lol. Prenatal yoga? Diet tips? I'm always hungry lol