Well yes, it is possible that you could be pregnant but it is also possible that worrying about it has delayed your period.
The best thing to do now is to take a test, the sooner, the better. Then you can decide what is best for you if there is a problem.
If the test is negative, yet you still haven't had a period in another week, I suggest testing again. If you still get a negative result and no period, it is worth seeing a doctor just to be sure all is well medically.
Chances are that everything will be fine and that your period is delayed because of stress; we have all gone through that.
Other reasons could be new medication or illness, even a change in your normal schedule. There are so many things that can change your normal cycle, but I do realise how worrying it can be.
I'm not here to lecture you but having unprotected sex wasn't your smartest idea. I know it's easy to get caught up in the moment, but next time remember how you are feeling now and be safe.