help calculating how far along I am

Elizabeth

I had a miscarriage and a d&c; in January. My Dr told me it was OK to start trying. Almost all of February I spent it spotting on and off and it was hard to tell when I got my period. I started trying to get pregnant March 1 and got a positive pregnancy test March 18. It was confirmed by a blood test I am indeed pregnant. How far along should I be? Serious answers and no rude comments please.