Why won't my Computer connect to my WiFi

Question

I recently came home from my first year of college. At school I uesd my Macbook everyday and connected to the school WiFi just fine. I came home and my computer seems to hate the WiFi here. That's not the bulk of it, though. The macbook is pretty quick to solve the problem and it gets connected. My iMac, which I leave at home year round, has barely connected to the WiFi since i've been home. Every time I get on it's a struggle to get it to connect. I have sat there for 45 minutes before I've given up. The only way I have found to make it connect is to jiggle around with the wifi. I turn it off and back on (on my computer), I disconnect and reconnect. I try connecting to the extention (which is further away but has just as strong of a signal reading). Like i said, it works fairly quickly on my macbook but on my imac it takes eons. The only thing that fixes that is resetting the router. Since the whole house is usually using it for Netflix and stuff I try to avoid that.
My theory is that the Extendor has somehow confused my computers. I didnt set it up so I dont really know how it works. But unles both of my macs contracted some sort of virus then I'm out of ideas. If i could i would run an ethernet cord up to my room and bypass the darn wifi for now, but that's not an option.
I was just hoping that someone out there would know what's going on. maybe have a solution. Im an idiot when it comes to internet. I know noting about ip addresses and the like. I dont even know what the ip address for my router is.
My iMac is running 10.8 my macbook is running 10.9. latest updates on the macbook (imac wont connect long enough to update). thanks.

Answer 1

Apple's Wireless Diagnostics may supply some additional helpful information.
To use it, hold an option key while you click your Mac's Wi-Fi icon, and choose Open Wireless Diagnostics...
The following authentication dialog will appear:
Authenticate with your Admin password, then click the Continue button in the following:
The network analysis and diagnostic tests will take several minutes to complete:
When it completes, if your wireless network is functioning properly the following will result:
If something is amiss, supposedly the results will be different and you will be presented with helpful information.
Assuming your connection is "working as expected" select Continue to summary and click Continue:
Ignore the pre-populated text field, which is provided as a place for you to type in additional information should Apple ask for it in the course of obtaining technical assistance from them. Apple has no way of knowing where your router is located in your home, and certainly doesn't know if you even have an upstairs bedroom closet.
Click Continue.
The next step will also take a few minutes:
When it finishes, you will be presented with a summary that may or may not be useful to you. Let me know if it is.
The WirelessDiagnostics-xxx.tar.gz file deposited on your Desktop can be dragged to the Trash, or you may wish to expand it and examine its contents. It's up to you.