craftgrrl | the disappearing stitches

ok I need a word of advice from experienced or even competent crocheters...

I just learned how to crochet a few days ago and I really enjoy it (im at the end of my pregnancy and busy work makes the hours pass). My glitch is this, the scarf I am attempting has now begun tapering no matter what I do. I keep losing stitches!! I have counted them and somehow I get from 23 in a row to 21 and I have no idea how. I have pulled it out and started over a gabizillion times. When I know I need to go just one more loop there doesnt seem to be one left...does that make sense? The funny thing is I didnt have this problem with the first half of the scarf then towards the end I realized my scarf was shrinking in width. Its like I forgot how to "turn around" so to speak. I really haven't founf anything useful in my little instructional book...does anyone have ANY idea what I might be doing wrong? hopelessly,
Sarah