could i be pregnant.?

It is possible to get pregnant from having sex the day after you get off of your period. I have heard the no's and the 7 days before, 7 days after. I've heard that you are the most horny when you are most fertile. I am typically most horny right after my period, not before hand. My husbands been in korea for a year and a half and got home on my last day of my period. We had sex the next day, it has been about 3 weeks since then and I am having symptoms of being pregnant. I have had a child before so i kinda noticed them right off the bat. I never get really tender breasts before my period comes and i have maybe 5 days before my period should arrive. I took a test and it came back negative, yet I'm tired all the time and i eat very little and feel very full. it hurts to have any source of pressure on my lower abdomen. the doctors had kept giving me mixed times for when i got pregnant, even at the beginning. Had one ultra sound, and they said i was on track for one date and it corresponded to my last period, then had a second one and they said i was a month off of the date. Anywho, is it possible that i got pregnant after my period. I don't typically feel horny any other day besides for a couple of days after my period. I know it's a hell of a question.