Had Sex, Having Tenderness In The Breasts, Cravings. Pregnant?
Given that you have been using the condoms with ejaculation, pregnancy is very unlikely. I am slightly concerned, though, there are times that the intercourse is unprotected. There is the slightest chance that there is some pre-ejaculate present with sperm that could make it into the vagina. While this is unlikely, it is a slight possibility. This is not meant to panic you, as the chance of pregnancy still probably remains extremely low.
With regard to her delayed cycle, if she were pregnant, the test should be positive by now. She should do a test now and again in 1 week. She should do this whether she gets her period or not. And yes, stress can affect ones cycle, perhaps delaying ovulation and delaying the onset of the period itself.
Her symptoms are likely cycle related and are typical of the second half of her cycle. If she were pregnant, these symptoms would not quite be present yet.
I hope that this helps. Please ask if you have additional questions.
Good luck!