Mommy help!

I have a 5 month old son and whenever he gets cranky to sleep I can never get him to sleep I shake rock hum sing move back and forth even have a rocker that does it by its own he never wants to be on top of me never lay or anything I don't know what I'm doing wrong he always like to stand but if he is tired why he never lays down I feel like a horrible mommy and it's my first baby ...