in the rush to brand OP as an addict several posters missing the fact that OP says she takes the prescribed dose of six daily to deal with the pain, but is coming up short, and that a box which should have contained the prescription amount of 168 and despite being labelled a only containing 68, actually only contained 20. That was a sealed box.
So, if OP is telling the truth and no one else has access, then the fault lies with the pharmacy. If l were OP, and sure of my facts, that would be the starting point, as well as informing the GP, as they are responsible for issuing the prescriptions. If they won’t cooperate l would involve the police. But this being mumsnet, the stance seems to be that because OP has been on the drug for a long time, she must be addicted and is trying to cover her tracks. Quite why anyone would think an OP would come on a public forum and seek advice for shortcomings on prescriptions for controlled drugs if they were taking them themselves is beyond me.
So instead of advice on a course of action to actually resolve the situation, in typical MN fashion, the thread goes down a rabbit hole. It’s quite possible that OP has needed these drugs for three years and still needs them, otherwise the GP wouldn’t be prescribing them on repeat. It’s also possible to function normally on strong painkillers once you are accustomed to them - people who live in pain do work, and yes, this drug is known to be addictive but OP appears to be sticking to the prescribed dose. And the drug is one of the most abused and has a street value, so it’s entirely possible that someone at the pharmacy is stealing them.
OP, involve the pharmacy, and your GP. Stand your ground if you’re sure of your facts and if you get no answers, inform them that you are involving the police. It’s the only way to get to the bottom of things.