Why do I have pain in my arms when I need to pee

If a Western medicine doctor is unable to answer this question for you, you may want to consider having an acupuncture treatment and asking them about this. In Chinese medicine, the meridians are treated, and this condition is sounding to me like it could be associated with a meridian. It may be worth checking out.

@gonzales72 I have never heard of heard of this and I don’t understand how they could be physically related. But as @jkathy pointed out they could be according to Chinese medicine and the theory of meridians. My daughter is a massage therapist and did some study in Beijing, China (where the summer Olympics were once held). She helped me when I had a terrible stomach issue by massaging my legs. Apparently there was a connection between these different areas according to this meridian theory and what she learned from Chinese medicine. At that same time I also tried acupuncture that my daughter recommended but noticed no change whatsoever.
Another possibility comes from a psychological perspective (my area of professional expertise). Sometimes two seemingly unrelated events occur within a similar timeframe and end up becoming psychologically related (unbeknownst to the individual). This is one of the principles behind the development of phobias. But the good news is that it is also a principle involved in behavior modification. The stimulus, response and consequence can be engineered to affect beneficial change. Sorry to dump psycho babble on you but it is my background.
Another idea you might find beneficial is this. There is a book available at Mayo Clinic Press all about the types, causes and treatments of incontinence. I have struggled with incontinence myself and found this book to be helpful.
Last but not least please know that you are not alone. You’ve seen how @jkathy and I chimed in to this discussion. Hopefully more members will have input soon.