Some people get their periods throughout their whole pregnancy. All women are different.
But, you were due for your period only a few days after you had sex, so of course you still would have had it either way. It doesn't matter if he was only "in you for a little while" it only takes a second!
But, anyway, I would not stress too much yet. With the timeline you gave you are getting close to being due for your period, but are not late yet. Just try not to stress as it can make your period late.
Also, after you have sex for the first time, a lot of the time your periods and cycle can change. So, you could be lighter or heavier, or late, or early. It is hard to tell. But, relax give it about a week and if you still do not have your period, then I would take a test. Good luck!