The short answer is that yes, the frequency of your catheterizations is causing trauma to your urethra, which results in the build-up of scar tissue over time.
The scar tissue will cause the urethra to get narrower at the sites of the scar tissue, and you will probably need an outpatient procedure every 1 - 5 years to dilate the urethra back to it's normal size (typically a size 22 - 24 catheter diameter). The outpatient procedure takes about 15 minutes. After a certain number of those procedures, most urologists will recommend that you get a shunt installed to replace the scarred areas of the urethra. I'll probably need to get a shunt down the road, also. For now, all I can suggest is to use plenty of the lidocaine anesthetic ointment, give it a good 10 minutes to work (if possible), and use a smaller-diameter catheter like a 14 French or a 16 French, because that will help minimize the pain, trauma, and scar tissue formation.
You can get a plastic syringe from your urologist, specially made to squirt the lidocaine ointment into your johnson. Then use your fingers to work the ointment down the shaft, to cover the inside of the urethra as much as possible. Maybe give it another squirt, what the heck. Also put a big dab of lidocaine ointment on the tip of the catheter. Every little trick helps. (By the way, ask the urologist for two of the special syringes, so you have an extra one.)
Hang loose, bro.
_