Fell on butt, worried! Please help

I am 16 weeks and I was just playing cards with my husband and went to sit down in the chair and missed the chair and fell on my butt. It hurt a little but not horribly.  
We used the Doppler and heard the baby but I'm just worried that I hurt the placenta or something? I fell on carpet but I'm still just worried...anyone had this happen or have advice/ consolation?