After 3 months of no sound, and trying EVERYTHING suggested on these pages, I have finally fixed the problem!
I bought an iPhone 4S USB charging port dock block connector for under a fiver off eBay, and got a friend to remove my old one and put the new one in, just by following a video on youtube!
I tried cleaning the docking port as suggested, blowing in it, using compressed air, switching the do not disturb button on/off, restarting/rebooting, asjusting every single bloody setting on the phone and I even took it to the genius bar (who weren't much help) just wanted me to pay over ÂŁ100 for new part)
Turns out the red indicator was on which means it's water damaged (even though I never take my phone into the bathroom and even have a special case for my phone which protects the docking area).
But now my phone works perfcetly, I have a ringtone, message tone and other alets and I can listen to music and watch videos now without having to have my headphone in...YIPPEEE! I cannot tell you how happy I am!!
Surely apple should design a phone that doesn't get water damaged so easily???
Anyway, hope this helps you!