I think you're probably holding your needles in such a way that you are knitting on the inside rather than the outside. The first 3 rows after joining you wouldn't notice because you are doing knit 1 round, purl 1 round, knit 1 round....when working in the round this type of pattern forms garter stitch which is the same as your previous 4 rows of knitting all stitches, back and forth.
The problem comes with the next row. Take a look at how you're holding your needles. You need to be holding the two needle ends of your circ closest to you with the right side of the work facing you. I think you're probably holding the two needle ends away from you (ie. with the cable of the circ and all the knitting between the needles and your body), therefore you are knitting on the inside of the tube rather than the outside.