One mistake beginner knitters (I too am a newbie) do is not changing the yarn's position when changing from purl to knit or vice versa.
When you are knitting, your yarn should be behind the needle and when doing purl, it should be above the needle. I am not sure I am making sense. You can have a look at the video section if you think this is your problem.
If this is not the problem, then just hang on. Experienced knitters on this forum will certainly help you!