why do you think you're 11 weeks pregnant? the doctor calculates pregnancy dates based on information you give so perhaps you stated an incorrect date in your interview. the last day of march was 15 weeks before the date you asked this question. that would actually make you nearer to 17 weeks pregnant as the date used is the first day of your last menstrual period rather than the actual day you have sex. an egg is usually available for fertilization approximately 2 weeks after your last period began in a woman with a "normal" 28 day cycle.
but wouldnt i be more than 11 weeks pregnant if it was the new guy i had sex with at the end of march? im 11 weeks