When you say MC....do you mean miscarriage (lost a pregnancy) or Menstrual Cycle? Sperm can live in a womans body, under the right conditions for a couple of days. I'm just confused as to what some of your abbreviations mean, so if you can clarify, we can try to help you figure things out.
Are you saying that you had sex on the 26 and she m/c on the 28?