This does sound very frustrating. A few thoughts...it might help to try and determine if the cause is physical, emotional, or both. Physical can be anything from hormone levels to nerve damage to post partum weakness, to more. I'd say cancer treatment in all its forms might be the culprit. If it was me, I'd review it first with my PCP, who as a rule tends to see "the whole person" more than my oncologist does. I also might address the issue privately. There are qualified sex therapists in systems like Kaiser who might help. And a quick look shows dozens of books on Amazon, so you are certainly not alone. If it is a pelvic floor issue there is excellent PT for that. You don't mention if you have a partner. Those scary conversations about intimate things can help, if you feel you'll get the support you need. With breast cancer one of my goals is to just continue feeling alive--and sexuality is part of that. I'm also trying to feel good when I can--walking, hot tub, massage, being outside. It can be a struggle, though, and you have my sympathy.