I have found the router to be the culprit, I found this by connecting directly to the cable modem (a cisco 2100).

But the rest of my family need a wireless connection and I don't really have the money to buy a brand new router, so I have came up with an idea but I just need you guys to check it and make sure it will work before I buy anything.

Basically I will buy an 8 port ethernet switch from there

The setup will be as follows:
Cable modem>ethernet switch>Wireless router + my computer

So basically if you can't understand my diagram what I want to know is can I plug a cable modem into an ethernet switch, plug the router into the etherent switch to make the connection wireless for my family. But then have another cable from the etherent switch that goes to my computer so I can connect directly to the modem instead of using the router.

Fast responses would be appreciated as if it does work I need to buy the switch today.