I just found out I'm pregnant and my doctor asked when my last piriod was. That is how he estimated how far along I was he said 6 weeks but the first time I had intercourse was almost 4 weeks ago I haven't slept with anyone in 6 months since this date so i know the doctor is off by a couple weeks and so is this app why do they try and tell how far along u are by your last piriod ? It's so inaccurate