some pregnancy tests dont detect it until you are like 5 weeks. i knew i was pregnant with my first before a test could even tell me. sure thing 4 weeks later after being 2 weeks late i got a positive. biggest thing is dont stress about it. the more you stress the more you make your body think you are. best of luck to you and if its your time it will happen!!!
some people get pregnant the first few tries, others dont, everyones different. if your period is regular then yes its definitely possible. id wait another week (or 2 if you can hold out that long) and test again. that way youd be 4 weeks late and it should give you a definite answer then. good luck girl!!