Anesthesia problems

I have natural chestnut/auburn colored hair. I'm supposed to go for anesthesia to get an IUD fitted but I'm extremely anxious because whenever I get anesthesia it never works. It's quite an invasive prpcedure. My natural hair looks brown a lot and you can see a lot of the red tones in light but I carry two rare mutations on the MC1R gene. In the past, doctors/dentists haven't given me enough anesthesia for procedures and I felt EVERYTHING, which caused me to now have a phobia of medical procedures because they were so painful. I'm super anxious because the last time when I could feel the IUD fitting I felt it and it was so painful that I threw up. I've also had toothache for the last four years and I haven't been to the dentist because of this. Does anyone have any advice? How do I explain my situation to an anethisist?