I have had problems with the left side of my labia for years. I have had numberous biopsies. My genocologist keeps telling me its an allergy. I have chronic itching, burning, swelling, and occasional lesions.
I have also been to a dermotoligist and urologist. I am using a cortisone cream but it has stopped helping me. I don't have pain, but the other symtoms are driving me crazy. I hope someone will have answers for me too.
You are right to try to rule out the Bartholiln's gland as a possible cause of your pain. It would explain the pain being on one side and affecting the labia as well. From other posts I've seen, doctors don't always take seriously patients with this problem unless the gland balloons up and causes you so much pain they have to deal with it.
See if you can better pinpoint the locus of the pain. Also, salt (sitz) baths will often help alleviate pain if it's the Bartholiln's gland. If you become convinced it is the gland then take your evidence to the doctor and insist on a course of antibiotic treatment. That's what they do when the glands become seriously infected and there's no reason to think it wouldn't help you now before it gets that bad. If it does help, you'll also know how to treat it if it comes back.
Good luck.