Had to add a comment to this.
Since for as long as I can remember, I have had a syringe phobia. I say syringe because I don't mind needles themselves, I like getting tattoos, I used to (WARNING THOSE WITH NEEDLE PHOBIAS!) put embroidery needles under my skin and pretend I was Edward Scissorhands (Edward Needlehands), and have had my lip pierced twice, my eyebrow pierced twice, an industrial, and four lobe piercings. But, attach a syringe to it, and it was splitsville for me.
It was so bad that at one point, I had to be held down by my mom, and two nurses while they tried to draw blood from my arm when I was really sick.
What really started to help me was giving blood to the American Red Cross, not only was my blood (A+) going to someone who needs it, but I also got free stuff at the end, it was a great motivation because I like 'prizes'. When I started therapy, while we talked about transitioning and I got my T letter within 3 months, we did a main focus on my phobias. I had expressed that I wanted to do injections, and had a phobia with them. He's certified in EMDR, and when we used that on my syringe phobia (and my spider phobia), it seems to have helped. It might be something to look in to, but if really you're having trouble with injections to the point of not able to do them, I would talk to your doctor about other forms of hormonal delivery. One of them might appeal more to you, and won't be as stress related.