I also had a fear of needles, blood and dentists. I passed out several times because of this. When I was pregnant the first time, the Consultant, having had dinner the previous evening with the Consultant Psychiatrist, sent me to him to see if he could help. He took me back to the first time I had passed out, which was when I had my Polio Jag at 11yo. I had it at school, having stood in a long line watching others get theirs. Returned to the classroom feeling hot and dizzy. Teacher told me to put my head between my knees and helped me take off my blazer, revealing that my blouse sleeve was literally soaked in blood. No one else in the class had this happen.
Psychiatrist, explained that this incident had triggered the phobia, made me think that needles/blood meant I would bleed to death. He decreed that I was to have no more blood tests at the clinic for the time being, but at my next appointment the new Doctor declared this to be nonsense, said that the more blood tests and injections I had the better - I would soon get used to it. He then proceeded to ram the needle into my arm, it broke and my blood shot out all down him and me. He walked out and the lovely big motherly nurse extracted the needle, comforted me and stopped the bleeding.
Why have I told this story in all its gory detail? Well partly because I now can picture the scene without feeling sick and partly to illustrate that it was this horrendous incident that cured me of the phobia, because I did not die, went back to work afterwards, and have been able to cope with 2 births, a miscarriage, dental treatment and the draining of a myriad of breast cysts, thereafter.