Well thanks for all the replies. I an very inexperienced at this point with ATC, and I can imagine with the "jitters" I still have, it wouldn't have been difficult for me to miss the three little words "fly runway heading", or even file a different departure that what I put into the fmc. . I'm likely the culprit, and going forward i'll "fly the clearances" as suggested and listen to what they actually say- rather than what I expect them to say. Good Info, thanks again!
So, I was out of LAX on DOTSS2 which takes you west a ways then left turn to come back around east. I got barked at by ATC for making that turn- I didn't debate over the comm but I was flying a procedure, was I supposed to get permission to turn? Joe Connolly KSTL