Could I be pregnant?

I started taking birth control almost 2 weeks ago. My doctor said I should be good after a week of taking it. However, I had unprotected sex BEFORE I started taking the pills. It was like a few weeks I was prescribed the pills. The dr had me do a pregnancy test but it was negative. However, I am starting to show symptoms and my boyfriend is starting to pick up on that I might be pregnant. My period lasted 2 days but was abnormally light. I’m sick to my stomach. I have headaches. I have never been on birth control or been pregnant so I don’t know the difference... I’m tired a lot. I have no energy. I’m scared out of my mind.

Update: I am now starting to spot and I am in my fertile window