Thank you for your question.
It appears that you had protected sex. If your boyfriend ejaculated in the condom then you will see it, because the condom catches the semen and protects you from pregnancy. Was there any time that you engaged in sex unprotected- without the condom? You have 2 negative pregnancy test, which support you were protected.
Many different factors can affect our menstrual and cause it to be delayed. Hormone imbalance, stress, etc. You are not going crazy. Try to relax and see what happens within the next two weeks.