That sounds very painful and I am sorry that your are going through this.
My guess is that this may be related to toxins.
Digestive issues can effect all areas of the body.
This is where I would start to detox if it were me.
I use several internal detox methods:
Home colonic Dr. Schulze F1 & F2 (Uny on Natural Healing forum has great similar products for these)
Chlorella (I pulverize my own for better absorption). Chlorella is one of my favorite food supplements because it has so many detox and health benefits.
How is your diet, stress level and what is your overall health regimen?