You've joined a recording forum, and that's not really the kind of mic we have experience of but with a mic of that price range, quality isn't going to be great anyway, BUT, I suspect it's more of a user thing. How far are you from the mic? Remember that these things are likely to be a cheap dynamic capsule inside, as it doesn't need power - so small changes in distance from the microphone produce large changes in volume. Perfectly normal, and the tone changes too. If you keep it at least 6" from you mouth, the changes in volume as your head moves get less obvious, and the tone stays more constant. However - the output level is then quiet and you need to add boost in the software, and this usually introduces noise on a cheap computer 3.5mm mic socket. We can't comment more until we hear it? You could always put it on youtube and let us have a listen?
Now the bad news - if the headset mic also has the same problem and this remains at a fixed distance, it points to your computer. If you record into audacity which is fine for this purpose, and see the level radically changing, then something is probably wrong. It could just be automatic gain control - is this a tick box item anywhere? AGC? It could be a permanently on compressor or something, although that's unusual. You really need to plug it into a different computer and test that. If that does it too - its the mic. If that is good, it's your computer.