It is possible, any time, any day u have unprotected sex plus no birth control pills...It's very possible.
But u said that u eat more then usual, always tired and stressful? Well these could be just that u are so scared and stressed. Eating more than usual always happen to ppl who are stressed out, and always tired? Yes that happens too. My guess is that u are so stressed so u dont do alot of things that u used to, so u are not as active, and when ppl are not active, they feel tired all the time, and just want to munch on things..
But to be sure take a preg test and know for sure.
Good luck to you!!