I have a simple and very beginner question here. I am a new knitter and in a class learned to cast on 30 stitches to start making like a wash cloth that needs to be 8 inches long. My problem is when I got home and was just knitting up a storm I noticed my piece getting wider.at last count I had 46 loops not the 30 I started with.i have no idea how thats happening.
Welcome to knitting and to KnittingHelp. There is a Sticky tread on the first page of the “How-to Questions” folder called “Mysterious Extra Stitches-Look Here”. 
This is a very common problem for beginning knitters.
Sounds like you’re accidently creating new stitches, and thus increasing your stitch count. Most likely you’re doing yarn overs in the beginning of a row, or during the rows if you’re knitting and purling.
Welcome to Knitting Help!
That is a common problem for new knitters. It’s usually a case of accidentally bringing the yarn forward between the needles which creates a YO (yarn over) or knitting the stitch between the needles. It can also be cause by knot taking the stitch off the needle properly after knitting it. Look at the link Marilyn gave you. You’ll get it, it just takes practice. 
This is common. If it drives you crazy, you can k2tog a few times til you have the correct number again. Once you get the hang of it, you won’t have this problem anymore. It just takes practice.
Welcome, and good luck!
This happened to me as soon as I started knitting too, as it did to my sister. So, don’t feel discouraged! But I agree with Marigold…check the “Mysterious Extra Stitches” sticky thread…very helpful.
Happy knitting 
And P.S. welcome!!!