I do regular subcutaneous injections on myself with a 1" needle. I rotate between belly and thigh for injection sites, and obviously it’s not quite as deep as what you’re doing. But still not something I’d choose to do for fun!
I’ve found that sitting up in bed while I do the injection works best for me. And it helps keep my leg nice and floppy when I’m doing my thigh. I ice the area I’m injecting really well for a good 10-15 mins before I do it. When I first started doing it I’d also take an OTC painkiller a half hour hefore, because I’m a big chicken. But, I realized that I didn’t really need it, so I stopped doing that. It might help you if you’re anticipating pain, though.
I pinch about an inch of skin/flab and push the needle in there, then release before pushing down the plunger. I push slow with the needle. I know from doing IM injections with horses that it’s better to just jab it in there, but like I said, I’m a chicken. Since the area is iced I don’t even feel it pierce the skin. I’m using a 23 gauge needle though, which isn’t that big. I do have a lot of fluid to inject, and I tend to go slow with pushing the plunger down, rather than trying to get it all done fast. Remembering to breathe helps too (just like it does with riding!)
I don’t have anyone who could inject me - my DH wouldn’t be able to deal with it. So necessity has been a great help in figuring out how to make this work! Also, since I expect my horse to deal with shots, I figure that it’s only fair to hold myself to the same standard. It’s momentary discomfort that helps me acheive a much higher quality of life than I would have without the drug. It might help to keep in mind why you’re doing the injections, and what the injections do for you, rather than getting worked up over the needle.
For a while there I was able to schedule my weekly injection around a TV show I really liked. So I had a time limit for getting it done - I’d do the injection in another room, before I watched the show. And having some sort of treat to reward yourself with afterwards also helps. Just like with horses! I give my horse allergy shots, but he now knows he gets a treat right afterwards, so he’s gotten much better about it.