I agree with momof7. My GP did a few internal exams (finger & with a small telescope) which luckily at the time did not cause me pain. But once I was referred to see a specialist, my condition deteriorated massively within the "4 month" wait and I was rushed to see the CRS (I was willing to get a private appointment just to move things along as the NHS lists in my area were humongous and I hadn't even had a 1st appointment letter or an apology letter for such a long wait 4 MONTHS!).
Once in to see him, I explained how chronic the pain was and he did a quick visual exam (he explained his thinking out loud with a Jr Doctor there too) and said there was a skin tag - which is indicative of anal fissures and did not want to do an internal exam. I was then scheduled for an EUA (exam under anaesthetic) where he would have a proper look and decide at the time what to do, which ultimately came down to a Sigmoidoscopy, double fissurectomy, skin tag removal and Botox.
So in my advice as momof7 suggests, be honest with your CRS, I'm sure they'll see the pain in your eyes if you tell them. They're there to help, not to cause you pain. They're specialists in this area and see this day in and day out. GPs on the other hand need to see exactly what's going on in order to diagnose as best they can (Jack of all trades, master of none).
Hope this helps
Welsh x