What Causes Painful Abrasion Inside Folded Skin Of Labia?

Question: where do I start? the current problem is .. abrasion inside folded skin of labia. Very painful .. can hardly walk & sitting on funny angle with pads soaked in Betadine, Sudocrem & baby oil pressed against the spot, inside my briefs. I understand all the causes .. currently prolonged hours sitting at the computer then sitting again at home. Labia was stretched during natural childbirth & now, 32 years later, I can't seem to keep the muscles strong enough to hold everything inside up and where it used to be. Also ... due to spondylolisthesis I sit very straight backed so this puts all my weight on the vulva and squeezes it (I weigh only 8 stone 3 lbs) I had cancer at age 37, am now 65, chemotherapy brought on menopause at age 38 - 39. Have never had estrogen therapy because of the risk. I have no natural lubrication & haven't for 20 or more years. No sexual activity for 4 years now .. too painful due to these overstretched labia which would occasionally tear. Also living alone now and not in a relationship. I wear cotton underwear .. shower daily .. use mild body lotions. This is the second time in the past 4 years I've had it so badly. We've just had 15 days over 110 degrees. My health and fitness is extremely good. I walk a very active dog every day, sometimes twice a day. I don't smoke and drink in moderation. My diet is mainly fruit, vegetables, fish and white meat, a little dairy i.e. yogurt .. no sweets at all. Never. So, if you can suggest a topical cream, or medicated oil that I can purchase from the chemist, (in Australia) I would like you to rule out infection, sex, std's, poor hygiene etc etc For the past 3 days I've stayed home, used Bepanthen .. then Sudacrem ... now a pad soaked in Betadine. Please can you recommend a cream to heal the open sore? thank you, XXXX

Dear Doctor T, thank you so much for your response. What you say will help me, I know. However, I would like to have the brand name of any 'oral antibiotic' or any 'topical' application - cream, oil, or other - that I can purchase from the local pharmacy. There is no pus, redness or swelling. This is simply an abrasion, similar to a pressure sore, or a bed sore. I hope you will be prepared to offer further information to help me find the best way of treating this .. as it appears that I will need to self-medicate unless I opt for surgery. I don't want to have surgery. It's not that complicated. Even though I'm likely to be afflicted with this for the rest of my life, I would like to go to my local pharmacy and ask for a specific product, which I am asking you to recommend. thank you so much, XXXX