[Harmony♥]

As mentioned, being stressed out over several different things, as you are, can cause your period to be a bit late. You've started a lot of new things such as a new job that keeps you constantly busy, and dealing with uni preferences and other such things.

You used a condom, and from what you've said, it was used right. Typically when a condom is used and it tears or leads to an unexpected pregnancy, it's because it wasn't applied right. But from the sounds of things, everything went according to plan.

You could always take a test to be sure. Always buy in bulk so in case you're not sure of one test, you have another or two to fall back on. Once you find out the truth, you could go from there.