;-; I need help with the knit stitch!

[almighty Fluffy]

Okay, so I started knitting about three weeks ago, and I know how to knit, purl, cast off, and all that jazz..
But every time I try to knit the first row, I'd get this line inbetween the two needles. As I knit more stitches onto the right needle, the string of yarn inbetween them gets longer, and when I knit the last stitch, I have a huge loop connected to the last two stitches! And it's only the first row that this happends, all the other rows I can do fine.
I have no idea what I'm supposed to do about it, can someone tell me what I'm doing wrong, because I don't know how it keeps happening.