Put it under around your pelvis that is what my doctor told me to do
I'm not that big yet... Lol. But my doctor did say the lower seat belt strap should go under your belly across your lap for safety reasons. And the other strap should go in between your boobs on the side of the belly. In case of an accident the seat belt won't hurt your belly.
Ive tried that. Im 8 months pregnant with twins. It won't latch. Lol.