Worried!

I had been wondering why my baby moves more when I lay on my back and I just read that you shouldn't lay on your back if baby start moving a lot as it's because there's not enough blood flow. I was laying on my back feeling his movement as I read it and immediately turned to my side but I'm worried now. Aslong as I don't do it anymore will he be fine? Does it actually hurt he baby in anyway? 😳 I'm 19 weeks