Don't feel bad! I used to combination knit and I didn't know there was anything different about it. As I watched other knitters knit, I adapted my knit stitch to the front of the loop but it never occurred to me that I was still purling like I did when I knit through the back of the loop.
Then I took a class at my LYS and was told by the instructor that I was purling wrong! I had been purling like that for years and I was devastated. I practiced and practiced and now I knit continental but it wasn't until I found this site that I realized I had been combination knitting, not knitting WRONG as I had been led to believe by the well meaning instructor.
I do knit straight continental now, just like the Amy's videos -- I had to adapt my purl stitch to match my knit or else go back to combination knitting but then what do you do with all those patterns that require you to knit through the back of the loop in order to twist the stitches differently from the rest, like the famous Clapotis?
Oh well! The upside is that my gauge comes out much better when I knit continental as opposed to combined so I guess I'll stick with what works.
Happy knitting to all, however it suits you!