What size needle you using??
I stick in the leg, never bleeds...There is A LOT of blood vessles in your ass...Chances are your gonna hit something....And who know's if your gettin right into the muscle...Find pics of injection sites online, flex your leg and find where the biggest part of the muscle is...I shot my ass, but it's too fukin hard...Plus you cant see what you doin....
Im takin tren as well...I had that feeling happen to me in my chest...It nerves...I shot one time and was feeling anxious, and I got that airy fellin in my chest...Burned a little (acid refulx..)