Concerned mother question

I only feel my baby move or kick at night. Which is a couple minutes before i fall asleep. I'm 19week and a couple of days. Today i got off of work and ran to the bathroom as I've had to pee for a while now. I sat down and felt a little uncomfortable but i did my business and quickly hurried to get back to laundry. Upon standing up i swear i felt this completely roll in a full circle. I am just concerned because this has never happened before and he's still being quiet and not moving? Should i be concerned about the motion also, is there anyway that might tangle his umbilical cord? Just wondering cause i dont think i can do much but apologize to my belly for making him do a gator roll.