BFP today, how far along am i?

hi ladies, i was just wondering, if my lmp was 3/7 how far along am i, is it 3 wks or 4? my period would be due about fri, since my cycles are 27 days. and im almost sure i ovulated on cd 12. i tested with 3 different tests, all came up positive today. i am so nervous, whats been your experience with your 1st pregnancy? thanx so much!