I fixed it.
To anyone else having the same problem:
1. Shutdown the phone.
2. Disassemble the phone. There are plenty of tutorials if you don't know how.
2. Find this connector and unplug it.
3. After a few seconds, plug it back again (when you do, you should hear a 'click' sound)
4. Reassemble the phone.
That should work, at least did work for me. This is the second hardware problem I had (the first one was the battery not charging offline issue) and both of them were just fixed by detaching and plug in back their respective connectors. If I would have sent this to Sony i'm sure they would have asked me to pay a lot of money for repairing it.