Am I pregnant?

I had sex on New Years <a href="">Eve</a> with someone I do not know. On New Year's Day I had slight spottings but I was still terrified. I got my period the next day but I still felt paranoid about pregnancy. I went to the doctor but my problem is that I drank water which could have diluted the test making it say that I am not pregnant. I took Truvada immediately on New Years Day (Truvada prevents HIV). Am I pregnant?