I second the home doppler. I purchased the one from Sonoline B, through Walmart for 45 dollars. Best investment! I am 11 weeks now and this is the first pregnancy I've had at age 30. The machine picked up the baby's heartbeat about 10 weeks in. :) I use clear aloe Vera gel with it, as it is much easier to find a heartbeat!
I brought an awesome fetal heart monitor off of Amazon, and with those, you can also hear the baby's slight movements...that way I could listen and check anytime I wanted too. It came with the gel and everything. Its worth the few dollars if it will ease your mind. It has a colored screen that digitally gives you the babys heart rate, and comes with and AUX cord and head phones....about $100 (+shipping). It could help with the worry.
If the doc said all is well m sure the baby must be fine. My first one used to be inactive one day and super active the other. I know how it feels...but don't worry too much...even mild movements are fine. Its better to get the heart beat rate checked regularly if u r still concerned
Did they give you a us when you were in or at least listen tk the babys heart beart?