My microphone doesn't work unless my headphones are plugged in.

I've had this phone for many years now, and I've not had this trouble before.

I tried looking it up, but my problem seems to be quite different to other similar ones, so I've decided to come on here.

Basically, when I make video calls on Skype or Facebook, my voice cannot be heard unless I am using headphones (through my headphone mic).

This is also the same with taking videos, no sound can be heard when I don't have headphones in.

Although, when I make phonecalls from my contacts, my voice can be heard on the other end, and I also tested it on my voice recorder app and the sound was perfectly fine, so it can't be a hardware problem.

I've also checked the permissions for these apps and the microphone is allowed.

Does anyone have any clue on how to fix this?

Thank you!