Injections are very small nowadays.
I was with someone in hospital a while back that was absolutely petrified, but he did it with a bit of encouragement. He was given the pen to try and put it in, and by the time the nurse came back he had done it with a bit of encouragement from me, and he admitted he didn't feel it go in!!! He even left the pen in his leg to wait for the nurse to see.......he was so pleased with himself. He wasn't a kid either- he was over the age of 25!
The other thing is that there is loads of places that you can inject-you don't have to do it in your stomach. I always did mine in my bum, and I was very naughty and only did them in my left cheek of my bum, as being right handed it was easier for me. I never used my belly. I would use my legs and arms. Even though I was naughty by not rotating as instructed, I am very, very, very lucky as I have not had any bad effects from this to my skin. I do advise that you rotate them as instructed.
To keep skin nice and supple I have always massaged baby oil in over my whole body after a bath (except my face). I use cannulas now, as I am on a pump, and I still use my legs and bum both sides in preference to my stomach. I am lean and a size 10 and no fat, just good muscles.
I too have an awful fear of injections....I have only ever had one injection in my mouth whilst being awake, and it took me 42 years to get the courage for this!! Ambulance people have tried previously to put intravenous injections in me, and despite being clasified as in a diabetic coma, I still lashed out and hit the Doctor that was accompanied by 4 paramedics at the time!!!! (25 years ago!!)-as I knew they were trying to put a needle in to me.....
I have to say that the needles nowadays are so, so, so tiny-4mm is so small compared to waht we were offered 25 years ago!!!! They are the vast majority of the time totally painless......
Hope this helps, and good luck if you have to have them. You can do it. Honest...