I hope you have discussed the lightheadedness with your doctor. It is not something to take lightly (no pun intended). I went through a round of this last spring and summer. It was accompanied by fatigue and occasionally an off balance feeling. My doctor did a round of blood tests and we discussed medication, but then I remembered how I felt years ago, before being diagnosed with allergies and going through years of shots. I went to see an allergist and sure enough my allergies were acting up. Medication helped but had side effects, so I started shots again and now I am doing much better.

I still have bouts of lightheadedness but much less frequently and I believe that to be caused by stress/anxiety. Pain can certainly cause stress/anxiety; add other stressors like trying to find the right treatment, paying medical bills, trying to complete normal daily activities, and the normal types of stressors of everyday life and your body will respond in a negative way. I tried drinking more water as you mentioned and that is necessary to prevent dehydration. I tend to eat and drink less when stressed. Of course, doctors will prescribe meds for stress, but they have side effects you want to avoid.
I have found mindfulness to be very helpful. I didn't have formal training, just got an app that describes it well. In addition, I had developed a fear of falling again and hurting another part of my body and creating a new CRPS site. Like you I was afraid to cross the street........just what we need more stress! So in addition to the mindfulness I use a pretty cane when I need to go out and about.....even on my good days. It is like a security blanket.

Before I was able to begin ketamine infusions, one of the requirements was to have a tilt table test and see a cardiologist. Based on results of the test and past episodes of fainting, the cardiologist diagnosed me with vasovagal syncope (fainting caused by certain stressors.) One thing he told me really helps. If you feel lightheaded while walking across a street, cross your legs and squeeze so that the blood that pools in your legs is pushed back into circulation. I have never needed it in the middle of a street, but have used it at home. Of course the other thing is to raise your legs above your heart level.

Good luck with your attempts to deal with this lightheadedness. Get your doctor's OK before you try to self treat. The last thing you want is to ignore any potential serious problem.

Shay