Try muffling the microphone with cloth, foam rubber, or some handy material just to determine that the microhone is picking up the surrounding sound. Or just cover the mic with your hand and determine if your friends can still hear youtube or in game sounds.
Likewise turn down your headset volume and make the same determination.
The objective being to eliminate the problem as microphone sensivity to surrounding sounds (i.e., the headset audio).
Right click the speaker icon most likely located lower right screen corner.
Double check both Recording devices and Playback devices. There are many Windows, Tabs, and properties to be found. Drill down through all of them to see if some configuration setting seems amiss.
Some of the settings are not all that clear as to what they may be do. Google as necessary.
According to the specification I found your headset has a 4 pole connector:
Headset - 3.5mm plug (4 pole) + extension cable - 3.5mm stereo and mic plugs
(Reference: http://www.hyperxgaming.com/us/headsets/cloud-stinger-gaming-headset)
Take a closer look at the physical audio connections with respect to the 3.5 mm plugs and ports (eg., TS, TRS, TRRS).
https://www.quora.com/What-is-the-difference-between-two-stripe-earphone-headphone-and-three-stripe-earphone-headphone
Could be that there is a mismatch along the way....