There's a problem with the Ethernet Switch

[pscythian]

I'm experiencing a strange problem
When I connect all my computers directly to the router, The internet speed is normal as It should be
But when I connect them to the router, VIA THE NETWORK SWITCH, The speed drops down so low. It's so annoying
And the strange part is that the internet speed drops down after 5-10 minutes
Is it the time to buy another Switch?
Or something can be done bout it?
HELP ME PLEASE, PEOPLE
THANKS