yes, your needle length is cutting it too close....
you need a few mm's (like 3-4) left out in case the needle breaks, removing a broken needle any other way is sheer hell and probably a surefire hospital (and lots of questions) visit....
and shooting anything more than 1cc of any lipoic (oily) solution risks an abscess from lack of penetration
and anyways, once you pierce the first 1/2 centimeter of skin, it rarely matters how long the needle is, you almost never feel any pain past the first part (so long as you don't hit a vein, or scrape bone)....