Anxiety medication - suicidal thoughts could happen...

So let me give you a brief history on me . Im a 17 old male and I have been having very bad anxiety for the last 5 months or so. I have been going to consoling and it has helped a little bit I guess. So on this past monday (2-6-12) I finally got to see a psychiatrist that day and got prescribed Sertraline 50mg. I only have to take half a pill for the first 10 days. So everything was fine UNTIL he warned me about the suicidal thoughts that could happen, he told me several times to not worry about that it is very rare and I was only perscibed a small dose so it would not be bad. So my anxiety began to kick in after I left at first I was very happy excited for life now that I could possible control my anxiety but in the back of my mind I began to worry about the suicidal thoughts. So yesterday night while in the shower I had a very bad panic attack and I began to think of medication side affects like suicidal thoughts. It was my first day taking my medication to so Im not sure that it could have caused it. I really don't want to stop my medication because I want to help control my anxiety. So my question is do you possibly think I could have over thought the suicide and am causing it myself or could it be the medication? FYI I will be calling my doctor in a bit to ask hi, just thought I would get people with the same situations advice