Use a pain scale, or a pain ruler
Remember that pain has an emotional as well as physical component. When you catch your thumb in a door you shake it and look at it. If it does not bleed too much but still wiggles and the pain goes quickly, then that is mostly "red" - physical. However the longer a pain lasts the more the emotional component becomes part of the problem.
The emotional component is made up of three aspects. There is anxiety and worry and typically we worry about two things. We worry about the "meaning" of the pain, why is it there, what is causing it, what is going on. Then we worry about the future and how the pain will affect us and our lives and our work and relationships.
Pain also makes us unhappy, although not necessarily depressed. This typically occurs in three ways. It affects us directly to make us miserable. It commands our attention, both consciously and subconsciously so we are listening for the pain thus hearing it louder and more often. Finally it isolates us socially.
The final aspect of the emotional component is the frustration that accompanies it. We become frustrated that it does not go away, that promised cures do not work, and that that life gets worse.
Thus, the physical component can be viewed as the transmission of the message up to the brain and the emotional component can be viewed as the unpleasantness experienced. Of course the degree of disability and the behavioural changes are subsequent phenomena.
Pain is felt, and travels up the spinothalamic tract to the thalamus.
Use WHO analgesic ladder
Combining two weak opioids isn't considered good practice.
Use the WHO analgesic ladder