If when you say you "took" a home pregnancy test on March 10 that came up positive, and you were wondering if that ruled out the sex on March 6 as being the cause of the pregnancy, yes it does. If sex on March 6 produced the pregnancy it would not have shown up that early on a home pregnancy test, it would have taken a couple of weeks, or at least 11-12 days.
Yes my next period was the 14th and also I toke a home pregnancy test March 10th cuz I was feeling sick n I knew I was pregnant I just had to make sure so guy #2 is not the father
Given how regular your cycles are, the notion that you ovulated and conceived on February 28 seems to hold up. Were you expecting your next period on March 14? It sounds like the guy on March 6 had nothing to do with the pregnancy.
Did you have any early ultrasounds that have given you an estimated due date? Failing that, it will be hard to tell. Are your menstrual months super regular such that your period comes every x days?