If the only time you've recently had unprotected sex was only five days ago, then the chances that your symptoms are caused by pregnancy is low, since it takes some time for a fertilized egg to implant into the uterus and begin sending signals to your body that you're pregnant. Those signals are what give you typical pregnancy symptoms like dizziness, headaches and lower abdominal pain.
The two most likely culprits for your symptoms are either ovulation or that you're about to start your period. Since I don't know where you're at in your cycle it's hard for me to say.
Ovulation happens about two weeks from the time your last period began and two weeks from the time your next period is supposed to begin. It can cause all kinds of not-so-fun feelings, especially that lower abdominal pain that's focused on either the right or the left side. That pain is caused by the actual release of the egg during ovulation.