help !!!

I had to recalculate my period prediction 3 times and still no period. I highly doubt I'm pregnant because I've had sex once this whole month with a condom and we checked the condom afterwards. I'm not sure why I don't have my period yet because it's usually normal. I haven't been really stressed lately but I'm starting to get worried. any ideas on what it might be ? what are the chances of me actually being pregnant ?