I have a curtain pole to install in our bedroom, I started drilling holes into the wall to install and put the plugs in but the drill stopped going into the wall. It's an external wall and almost feels like there is metal when I tried to continue drilling. I need to screws to be flush to the wall or they won't hang the curtain and I need the plugs to be able to go in. Should I get shorter plugs/screws? #diy