Im 22, married, and would like some advice.

My last period was Jan 1-5, normal like always. Sometime after that, maybe 2-4 days, I had unprotected sex. For the last week and a half Ive been sleeping and even napping all the time and I go a long time before I want to eat, I never finish all of my food, only eat twice a day,slight headaches, but I havent had any usual pregnancy symptoms like morning sickness. I started to worry that i might be pregnant but I started my period on the 28, (today) right on time. Its just very very light and dark brown with only light cramps. I usual have terrible cramps and a strong flow.

Is this just a weird cycle or could I be pregnant?