Welcome to HCM.
You are carrying near about 8 wks pregnancy
as your LMP was 14th Feb.
Your last scan reveals yolk sac
is not growing and same as before.
It may be due to late fertilization of ovum as you confirmed pregnancy on 3/11/12.
You have to wait more time and do tests like serum hCG
Also do a fresh USG next wk. If progesterone level is below normal,then need to take external supplements for progressing of pregnancy.
All thing do with consult of your gynecologist.
Take healthy diet with protein rich stuff, take complete rest.
For more information,mail me.....firstname.lastname@example.org