am I pregnant?

I had sex on the 22nd, 23rd and 24th of February, and my ovulation was on the 27th according to the chart. We used a condom every time anche checked whether it was broken afterwards, but everything seemed fine. I am now five days away from my cycle and from yesterday night experiencing heartburn and a bit of nausea .. also at the beginning of the week my nipples were a bit sore. I am starting to get nervous about this, do you guys think I might be pregnant?