It sounds like you are using a tin can on a string, if you get told you can't be heard in a phone call. It happens to even professional streamers.
It could be that you have a good quality headset plugged in, but your Windows computer is trying to record using its awful built-in microphone. It could be difficult to deal with.
You can figure it out here.
1. There is a tiny icon that looks like a speaker at the bottom-right of the screen.
If you click on the icon that looks like an up arrow, it will show you icons that have been hidden.
2. Click on the speaker icon and then select Open Sound settings.
3. The section labeled Input is where you can scroll down. Windows will show you which microphone is your default, as well as a blue bar showing your volume levels. Talk into your microphone. If the blue bar jumps around when you raise and lower your voice, that means it is working correctly.
4. If your computer is using the wrong microphone, you can change it by clicking on the drop-down menu and selecting a new option.
This method will only tell you if Windows is detecting your microphone, it won't tell you how you sound.
If you want to hear your own voice, Audacity is a free audio recording program. Select your microphone in the menu at the top of the program and hit record.