I am a new knitter and I had the same problem. I didn't know what was happening. I had at least 15 more stitches than I wanted. After posting here, I got the good advice to just keep knitting and not to stress about it to much. I was not pullimg the yarn down, and was adding a stitch each time I turned the needles. I bought some large needles and some thick yarn and just knit and knit until I got the hang of it I am getting better at it but still have a problem every now and then so I count my stitiches often.
Good luck and hang in there!