[monkeyhatfork]

like Erik and Evita said, the cramping will go away, as far as holding a straight line, that should come to you quickly as well, you may be using too much leg, not have enough core strenth, you want to make sure it's a full body movement initiated by shoulders then your legs and fin more or less just fall in line with the movement. All this will work itself out after you get a few sessions in. Look on youtube for dynamic video's I found the Peter Pederson 200m video very helpful when I was starting out. Relax too-if you tense up it will add to cramping