Yes, the best thing is get your phobia and reclusiveness addressed first.
You can always see a different GP, or even practice.
For pain killers, the UK counter-legal strength maximum is Dihydrocodeine, which has only just recently been made non-prescription.
Dihydrocodeine has a good chance of knocking you out, making you feel very bad dry mouth and even vomiting. DONT take more than one or the recommended doseage as it DOES have a strong effect.
I swear by it but only when needed as its miracle strength is because it is a 30% morpheine/opiate mix which means highly addictive.
You *MAY* be able to get paracetamol in addition to this but maybe not, (ask chemist) if it would be needed at all. DO NOT even consider taking anything stronger with it.
The top branded "neurofen plus" and such new versions of the previous-best drug (Ibuprofen) contain a codeine AND paracetamol (and/or sometimes caffeine), and this is where the CoCodamol (co as in dual, cod as in codeine and amol as in paracetamol) name comes from.
This is not quite the same as DIHIDROcodeine, which is much stronger and as such may not be suitable for paracetamol.
Of course, the second best thing is cocodamol or the branded codeine-paracetamol drugs.
Ibuprofen is the next one down, the miracle painkiller before codeine was legalized. The Caffeine enhanced versions work a little better ("Ibufen Plus" or similar brands)
After that there is Paracetamol generally, although this is not so strong on its own as it is not an NSAID (anti-inflammatory) and a lot of pain is usually a result of inflamed areas.
If Dihidrocodeine is not available without prescription and the other stuff doesnt work, you REALLY need a prescription drug.
There are also the likely-illegal methods in your country...
-marajuana is a great pain reliever. It is actually prescribed by clinicians in some western places.
-also, I work in the wrestling industry where we have to put up with a hell of a lot of pain (screw those who say its all a charade, you dont have to wake up and earn money this way) and torture daily, especially while trying to quickly recover from painful injuries. There are some shady doctors who can prescribe, or even you can directly obtain via online pharmacy sources, strong pain killers to help you out.
Be careful if you arent buying from your local Boots. Drugs from dodgy sources can be just as dodgy themselves, plus you don't get safety guides or advice with them. They can even do more damage than good, and in some cases are not even the drug you think you are taking. Some are faked placebos, and some are sub-par or even completely different drugs for different purposes. Faked drugs can even look identical with packaging and everything.
Its usually not worth it.
Yes, these drugs and the dope are highly addictive, but ALL painkillers are and are very dangerous to your liver and kidneys, and often just dont work after a while if you take them too often.
So exert caution....
Best thing is just overcome your fear and get to a good doctor who can prescribe something.