Does Facetime use cellular data if you have Bluetooth?

I connect my iPhone to the computer and get the bluetooth connection. Does this mean that i don't need to worry about data charges applied to my phone?

I believe that you still get charged with data, unless your on Wi-Fi

If your computer is pulling data from whatever service you are using then yes it will charge you. Just because you created a hotspot with your laptop doesn't cancel out the data charge coming to it.