Are you aware that when a doctor gives you the GA of the pregnancy (the number like 7 weeks 5 days) he is starting the count on assumed the first day of your last period, not telling you how many weeks old the embryo is? On the day the doc said you were 7 weeks 5 days along in pregnancy, your embryo would have been 5 weeks 5 days along. They count from the first day of bleeding the last time you had a period (or the assumed first day) because that is a big, obvious signal, not because they think you got pregnant that day. You got pregnant around March 21, not March 7.
I actually wasn't aware of it only till I went to a sonographer yesterday and read your post that I finally understood. Phewwww I must say I am relieved and I won't ever do such a thing again. Many thanks Annie