I want to weigh in on this because I'm in a similar situation and have been for 11 or so years.
I had heart surgery and somehow, in the process, I suffered a dropped right foot. That meant there was serious nerve damage that paralysed my foot and the pain was excruciating and to this day it is very often excruciating and virtually constant at some degree of intensity. I also suffer from bad back pain. The good news is the (foot pain/nerve pain) is because the nerves are still regenerating and healing so I compare that pain to Purgatory . . . a healing pain . . . that serves a purpose, rather than the nuisance pain in the back, which serves no physical purpose.
Both, of course, can serve a spiritual purpose if I offer it up but as Bob said, taking pain medication as needed, doesn't make your offering any less worthy before God. We, as Catholics, often look at suffering as redemptive but we also consider that Christ came so that we might have life and and have it more abundantly. The Bible tells us that one of the Old Testament Names of God is Yaweh or Jehovah-Rapha . . . meaning, I Am The God That Heals. Isaiah 53 tells us that
"By His stripes we are healed" (Isaiah 53:5)
This is also quoted by St. Peter in 1 Peter 2:24. While it is true that the primary meaning of this healing is spiritual, it also includes physical healing so we need to balance:
- our embracing of suffering for the sake of the Gospel and salvation of mankind,
- with the fact that God wants us to be able to function in order to serve Him.
God allows suffering in our lives, so as to give us an opportunity to exercise our faith in all circumstances but that's true of any circumstance God allows us to experience or go through.
Ten years after my surgery, I still take painkillers as needed. Now, I'm trying to lose weight and I'm walking and exercising. This exacerbates the pain and I find that I need to take them more frequently . . . all, of course, under the supervision of doctors.
As I said before, God wants us to function to serve Him. To the extent it's physically possible, He wants you to be self-reliant, productive, and able to serve others. That service to others may be limited to prayer but:
- If pain makes it more difficult to pray, or even think clearly, then not taking your pain medication is counterproductive.
- If the pain is what keeps you from performing your daily tasks, then that's preventing you from offering your daily tasks to God.
- Moreover, if the pain means the difference between more assistance from others, rather than less assistance, then you're preventing those who are helping you, from assisting others that might need it more and you could free them up, by simply taking your pain meds.
So, there is a balance you need to find. Be careful not to be too scrupulous and also be careful about not abusing pain medications.
Unlike years past when some doctors prescribed painkillers like candy, these days, doctors are very careful about what and how much they prescribe so consult with your doctors. Don't be a hero . . . as you may wind up becoming self-righteous. Remember, when we offer up suffering, we offer up and unite it to the suffering of Christ . . . and we always look to the Cross, Christ and Him Crucified. It is He who gives us the grace, the desire, and ability to bear all things and to offer them up to Him.
Our merit is only of value in so far as it is a response to grace, through Faith in Christ and what He did for us on Calvary. Otherwise our works are dead works . . . and that's the flip side of faith being dead without works.
Finally remember that your body is the Temple of the Holy Spirit. Therefore, you have an obligation to take care of your body, just as you take care of your soul.
One More Very Important Point!!
We are not medical professionals.
I happen to know more about this because of my personal experience but not taking your pain medications could also have other serious consequences. When we are in pain, our blood pressure tends to go up. That could lead to a stroke, heart attack, kidney function issues and so forth so as I previously said, our bodies are the Temple of the Holy Spirit. Therefore we have an obligation to not to harm our bodies in seeking piety. Our lives are gifts from God, not just to ourselves, but to others, so we must take care of ourselves.
If you choose to forego the use of pain medication, then make sure you're monitoring your blood pressure and heart rate. By all means discuss all your decisions with your doctor.
I hope this helps.
Warmly, Under His Mercy,