To begin with you can have all other computers in the house shut down so yours is the only one online then go here and run the test:
Speedtest.net by Ookla - The Global Broadband Speed Test
Then have all the family members bring their systems online and run another test...
Whats the results?
BTW, it would be handy to know the manufacturer and model number of your router, there are only around 1,000 routers and models and all are different.
Oh, and what Internet speed are you paying for? Your ISP?
We don't have
Nor are we