OP you mentioned feeling a "ball like" swelling at the entrance to your vagina. This sounds like it could be a Bartholin's cyst. If you can have a look in a mirror and compare to Google images, I would see a GP or call the Sexual health centre if you think it may be that.
I was experiencing a lot of vaginal pain a couple of years ago with clients, even if they weren't particularly large. These are the things I did to help:
1. Worked on really improving my oral skills and domination services so as to have less bookings which include sex (I managed to make oral-only and dom bookings well over 50% of my work)
2. Banned fingering completely
3. Experimented with different lubes - my favourite now is ID Millennium. It's also completely tasteless and ordourless. Lube before any penetration, always
4. Put in my FAQs that I don't like big cocks, and if a client turns up with something I can't handle, then we won't be having PIV. I would rather partially (or even fully) refund a client than put myself in such pain that I can't take any more bookings
5. Used BV Active pessaries after a busy day, leave in overnight (but wear period knickers to bed as otherwise it leaks onto your sheets)
However the thing that seems to have made the most difference is two-fold: stopping drinking alcohol, which was exacerbating my menopause symptoms, and coming off Depo provera. I'd been on Depo for over 10 years and vaginal dryness is a known side effect. I've never lubricated much all my life, no matter how turned on I am, so being on depo was like a double whammy (but worth it to never have periods.) Now it's out of my system, I've found it much easier to handle sex.