What's the best program to watch my bandwidth?

There is a Firefox addon called 'Net Usage Item' that can use various XML-based services on your ISP's network to extrapolate and display the data in your Firefox-based browser.

Otherwise, I would suggest bookmarking your ISP's reporting pages, or you will have to install something at the network level to watch the bandwidth usage, since you have used the pronoun 'we', I presume you're on a home network with other users and devices.

DeDav said:

I was hoping for something outside of any internet programs, specifically Firefox since it's been slowing down for me. If I do use Net Usage Item does it track everything on the computer, but it just needs to be viewed in Firefox?

It doesn't track anything. It will ask your service provider how much bandwidth you have used and then display it for you in the form of a bar on your browser wherever you'd like. You can click on it to refresh it, and it automatically refreshes periodically.

The addon doesn't support a lot of ISPs out of the box since it is mostly for Australia, but the concept itself is probably more what you're looking for and I would be surprised if your ISP didn't already offer something like it.

If you're looking to keep track of data usage on your PC alone, then specific software will do it for you, including what has already been mentioned in posts above.

160gb in 8 days is a substantial amount,
if you or someone else in the household is using bittorrent or utorrent you can set a monthly cap to include up and down traffic.
from the options/transfer cap tab