What Olahaldor says is quite true – OBS uses a separate sound level to that of your headset/speakers. You can turn your sound up and down all you want for your own personal output and OBS will still stay the same (very useful)

Use the microphone and output sliders in the OBS interface while recording offline to find a good balance – Might even help to tweak your mic a bit bac and forth to find a good balance between volume and static/background noise.