Most home grade routers do not have the capability in and of themselves to determine the volume consumed by the particular LAN devices. You can look at the DHCP page of most router's configuration and get the MAC address of all devices logged on and this will tell you what is connected. I suspect you have freeloaders hogging some of your capacity - especially with a wireless router.
I suspect you have lax security, have used the default password and user name, you broadcast your SSID, and you have given out your wireless access password to others who have passed it along. Alternatively, your use of default settings permitted people to hack in.
You need to tighten down your wireless markedly. You need to check the manual that came w your router to learn how to do these things:
1. Link to your router with a pc that is attached to the router via a wired CAT5 connection, not wireless connection.
2. Log onto your router by entering the IP address of the default gateway in your web browser. Use the router user name and password to get in. I suspect this is the default password. Change the default password to something that you document and that is not a common word or term, that is a mix of upper and lower case numbers, letters, and symbols. Document this.
3. Make sure your router cannot be configured by someone on the LAN via wireless link. Many routers do not permit wireless users to access router, but not all do. You must do this to keep hackers from changing your router configuration.
4. Change your SSID to something other than the default SSID. Use some name you understand but that no one else can recognize as yours (e.g. bob's wireless, or smithresidence, or your street address are particularly bad choices if your name is bob or last name is smith; you do not want a dead giveaway; conversely if your name is not Smith or Bob, maybe such an SSID is not bad as it at least does not seem to point to you). Record what you have done.
5. I strongly suggest you change the LAN subnet. Most use the 192.168.0.0/,24 or the 192.168.1.0/24 subnet with the default gateway (which happens to be router IP address in simple networks) as 192.168.0.1 or 192.168.0.254 on 192.168.0.0 / 24 or 192.168.1.1 or 192.168.1.254 on 192.168.1.0/24. Remember that a /24 means a 24 bit mask which is 255.255.255.0. I suggest for home routers at least a 26 bit subnet mask but I will not get into that here; I suggest that you use something like 192.168.23.25 for the default gateway with mask 255.255.255.0 which puts the router on the 192.168.23.0/24 subnet which is harder for hackers to guess. Make the DHCP range 192.168.23.50 to 192.168.23.75 if you have less than 15 devices to connect via dynamic IP address. I like to leave about 10 more IP addresses in the DHCP pool than I feel I will need. Remember that after you have changed the router IP address you need to log in using the new IP address after rebooting your pc (alternatively you can use command prompt and enter the commands ipconfig /release followed by ipconfig /renew if you are familiar with this).
6. Go to wireless security. Change encryption to WPA2 - preshare key sometimes called WPA2-PSK. Provide a strong preshare key (wireless access password) that is a mix of numbers, upper and lower case letters, and symbols that are not recognizable words. It should be at least 12 characters long. Record the password you have given.
7. Determine the MAC address of the wireless interface of all devices you wish to permt wireless access to your LAN. The MAC address is unique to the wireless interface of the device. Record each MAC address. A MAC address is a 12 character address.
8. Implement MAC address validation on the router security to permit only those addresses in the validation table. Enter the MAC addresses from # 7 above in the router MAC address table. Record separately the MAC address and the device for each of the MAC addresses.
9. Now go to each device, find your SSID, set the encryption for WPA2-PSK, enter the proper password, and you should be able to connect.
10. After all devices have been connected to the wireless, disable the SSID broadcast.
Now you have markedly tightened down your wireless and all should be a lot more secure.