Inconsistent Wifi speeds/How do I diagnose network issues?

[JZStudios]

My computer frequently loses internet speed to the point where it's no longer usable for ~15 at a time. Simple online blogs or things like the Google homepage end up taking a minute to load and sometimes fail to do so. The best I figured I'd try to diagnose it is moving my computer into the living room and hard wiring directly to the router and check the speeds there vs. my Wifi card. At close range (within 6 feet) the hardwired and wireless (Both 2.4 and 5g) give the same connection speed according to Ookla. Moving it back into my room the 2.4 is massively reduced in performance and the 5g is moderately reduced, but also spotty speedwise. Is this just a normal thing? According to the others in the house they don't have any problems.

For reference, the modem is a Motorola SB6141, the router is an Asus RT-N66U, and my Wifi is a USB 3.0 Linksys AE3000. There are in total 4 computers in the house with a smart TV plugged in direct to the router.

For further reference, the Ookla speedtest results are as follows;

Proximity <6ft

              Ping         Download       Upload

Wired     16            60                  6.85

2.4         17            60.42             6.54

5g          18            59                  6.77

Proximity <40ft   (results averaged)

2.4         60.3         16.2               4.13

5g          38            46.59             3.92

I'd like to know if I can solve this, because those numbers above (At distance) are higher than usual since everyone was out today. Anything that requires an internet connection is a crap shoot on whether or not it will work.