I wana cry!! ..pls help ..

I bought a $30 stud finder and its not working on ceiling. It beeps in the most random places! (it’s supposed to detect up to 1.5” depth, and it works on walls.) Tapping’s not working, even with the back end of a big screwdriver. No hollow sounds!! My ceiling sounds really solid all over. Can’t I place my pole just anywhere, in a slightly different place every day? Or use a bigger cardboard square/board on top to distribute the pressure? And put it up only for a few hours a day, then take it down? SURELY THIS WILL DO NO HARM??? 😲 Otherwise I think I’m left optionless! I don’t wanna ruin my ceiling with nails and my gut tells me it wont work anyway (and my instinct is usually right). Sooooo frustrated… who knew there was so much hassle! 🙁