Sorry to read of your issue. The most common cause of symptoms you describe in my experience is contact dermatitis. Coming in contact with something you are allergic too. Common irritants are soaps, detergents, fabric softeners, and panty shields. I instruct my patients to wash their underwear in Woolite, No thongs, use only Cotton underwear, use a hypoallergenic Soap like neutrogena, and do not use any fabric softeners.
I also treat them with a topical steroid Diprolene AF Cream. If the condition persist and does not appear to be a contact dermatitis, a biopsy of the area is usually warranted. A diagnosis of Vestibulitis may be appropriate and this condition is often treated with Timovate cream, a very strong topical steroid.
Vestibulitis, also called Vulvodynia, can be difficult to treat and you should look for someone in your area that has an interest in the treatment of this condition. You may find the National Vulvodynia Association, www.nva.org of help. JKM
I've been diagnosed with vulvodynea, and I share many of your symptoms (the touch test was killer for me) but I also have contact dermatitis.
I use cetaphil in the shower.
I use very small amount of "clear" detergents , and add a little white vinegar in the rinse cycle dispense I to get rid of any remaining soap. I don't use any toilet wipes or scented toilet paper, and I find a sitz bath in plain water can help alleviate the symptoms. My doc gave me a rx from a compound pharmacy for a cream containing lidocaine, aloe and an estroidial cream, which gives me some relief . Good luck!