You are doing something wrong if you can't draw blood. You're missing the vein some how. If you are scared, you should not be injecting drugs
I would not recomend shooting into any vein in your ass. That's begging for an infected abcess. You can IM, actually insulin syringes aren't long enough to reach muscle it's really a sub-q shot, but the high is no better than snorting
, honest. There's no reason to pop your shit when you could snort it and aviod all the risk associated with injecting.
Edit, if you decided to pop it, make sure you filter very well. Double filter even. Having solid particles under your skin puts you at great risk for abcess/infection.