Barry, I have had two catheters at the same time on a couple of occasions. For the urethral catheter I would ask for some instilagel and ask if it only to apply some in the tip of the penis, you can get it without prescription from a pharmacist. The suprapubic catheter wound just needs keeping clean with boiled water. Don't be surprised it the suprapubic wound gets infected and needs some antibiotics. On both occasions the stitch was meant to be removed after a few days but the GP practice nurse would not remove the stitch because it was too infected. Most people seem to leave the dressing off when possible.
I had a SPC fitted on two occasions once after a failed dilatation punctured the urethra and the second time was as insurance against a stricture closing up before having salvage RT. I don't recall either of them being particularly painful, they were definitely sore. I wonder if you pain is more from damage caused by the stone. The bladder spasms were definitely painful and at times were happening 40 times a day for a few minutes each time. Ask for some antispasm medication, it may take a few days to work, I have tried a number of different medications but found trospium chloride/ Regurin to be the best. Following a SPC change the catheter will either be in the right place and totally comfortable or in slightly the wrong place and annoying for a few days until it settles in the right place.
If the catheters were going to be in long term they would be left in for twelve weeks, the SPC one probably had a microbial coating. Nearly all catheters are licensed to left in for a maximum of twelve weeks. Routine changes vary from 2 to a maximum if 12 weeks. Frequency of changes will vary depending on how much sediment or encrustation builds up , I have my SPC changed every eight weeks.
After my dilatations they were usually left in for four weeks. When I had both catheters at the same time the urethral catheter was removed first and the SPC was left in for a couple of weeks but had a tap fitted instead of a bag, I then urinated normally and the tap was there there to release urine if I went into retention. I don't change mine myself, many people do change thier own.
When they punctured my urethra, urine was getting into the soft tissue of the penis and that was extremely painful and the penis did swell up. You could be getting some urine coming past the catheter and causing and issue.
Make sure you are drinking plenty. Constipation can stop the catheters draining freely. If both catheters are connected to drainage bags, you would be unlucky to get both catheters blocked. If you do have drainage issues get help. Don't be surprised if the urine in each bag is a different colour.
Hopefully it will all settle down soon. Always happy to answer any other questions.
Thanks Chris