Ok -how sensitive are the clear blue digital tests that estimate how far along you are? My period was suppose to be the week of Feb. 15th - I didn't have my period so I took a test on Thursday Feb 18th with the clear blue digital and it said negative? However I am pregnant now and the the doctor is going off of my last period in Jan. And saying I am 12 weeks but if I took a test mid Feb and it said negative I can't be 12 weeks right!?!? Please help! Thanks