Hi and welcome to the forum
I moved your thread in the general software section of the forum
A free (and portable, i.e. no installation required) bandwidth monitor is NetWorx
If you use a wireless connection, a possible cause of the too high usage check if there is someone stealing your bandwidth.
To check who is using to your router through the wireless connection you can check in the router settings: a list of all connected clients should be available.
See the router user manual to find details