I had similar problems to you using an experia headset with mike , it was a windows update that sent things haywire.
Go to device manager/ sounds and mic tabs then right click and uninstall drivers even if they dont have a yellow triangle on them. Windows will reinstall the generic drivers on restart.
In sounds/playback tab right click and disable the realtek digital output. just above the icon when using SPEAKERS you should see a green tick in the speaker icon , right click if missing. When you plug in your headphones the icon will go out and if you scroll down you will see a new one for headphones . when you swap between speakers and phones it takes a few seconds to find new device.
check properties tab on both headphones .... green jack highlighted and microphone pink jack. finally at bottom right corner where the speaker icon is change the tab to realtec high def audio , i have my volume at 50%