You don't need to aspirate I was told that's an outdated an unnecessary practice. I never aspirate and I get mine at a 90° angle in the center of the deltoid which is alternated to the opposite delt every other week. Been doing this for over a year now, never aspirate, no problems. Don't switch needles though, stick with what you've been using because when I tried changing gauges I found too many defects. I injected into my fat once because the new gauge size had an angle to the needle and boy it was very painful I had to go lay down for a solid 10 minutes until the burning stopped. I had also been switched to interlock barrel needle once and it did a sudden pop and fast injection which hurt for a few days so I switched back to my luer lock.

For ref now, I use 22 gauge 1 1/2 luer lock and I just draw it straight without switching gauge sizes because I was loosing my oil solution during the switch. The needle is still effective and doesn't hurt, I take care to not bend it or scrape it against the glass of the vial. (If you wanna switch tho you do you)

Also, sometimes you bleed and sometimes you don't. Blood is just a ruptured capillary in your skin and doesn't feel much worse than a paper cut in my opinion. If you're unsure about veins, search the anatomy of your site of choice and learn where the arteries are, not to mention study many injection guides. Hope this helps.