Could I Be Pregnant?

I'm almost 18 and me and an old guy friend of mine hooked up, this was 11 days ago, now I'm having some symptoms like sore/swollen breasts, increased appetite, fatigue, sometimes dull other times sharp pains in my lower abdomen, and sometimes I get them in my head too, and I normally get white sticky like discharge but now it seemed to get lighter, could I be pregnant? And when should I take a hpt?