Hey, don't worry, I did exactly the same thing when I first learned to knit... and I purled into the back of the stitch, too. I actually was trying to learn how to do twisted stitch patterns and realized the book was describing what I was doing before I even realized I was weird.
I've found that knitting this "wrong" way actually looks better if you ever knit on double-pointed needles, like socks.
Thanks for letting me know I'm not alone in my weirdness!
I had to concentrate on sticking my needle into the loop, not under the loop... if that makes any sense at all.