Apparently you've been adding stitches somehow, which is not uncommon for new knitters. The length won't necessarily be the same as the gauge calls for. That's not as important as the stitch gauge.
I would start again, just for practice, and count your stitches after each row. I wouldn't worry about gauge just now. Cast on some stitches and knit, knit, knit until you really have a feel for it and you can recognize what a stitch should look like.
If you're switching between knit and purl, often the yarn is in the wrong place when you do your stitch and that creates an extra one. It should be in the back for knit and in the front for purl.
Hang in there!