9 weeks, heartbeat? undetected..

christina • ChristinaMarie💅
I still have all symptoms of pregnancy , no odd or painful symptoms had cramping that lasted maybe 10 seconds and have been fine ever since. no spotting or blood or any signs of M/c I haven't had an ultra sound yet but they did try and check for the heart beat which was no where to be found. my doctor said that typically you don't hear the heartbeat untill 12 weeks ish.   he said the baby could just be "hiding" or just in there a little deeper.  currently they think I'm 9 weeks and that's going off of my last period date which was between July 4-15. 
should I be worried at all?
maybe I'm not as far along as they think so maybe there isn't a heartbeat just yet? I just don't know what to think &I am trying to not make any assumptions but it's definitely nerve racking. 
I have my next apt in 4 weeks on oct 17th.