Am I pregnant?

Last time I had sex(unprotected but he pulled out) was about 3 weeks ago. I have had my period last week. But for about this entire week, my stomach has been hurting. I feel like I need to throw up 24/7. Every time I eat and it is a little bit worse in the morning. My stomach feels so bloated and hurts. How do I know that I’m not just having pregnancy symptoms? I have no other symptoms other than headaches and nausea. But I’ve never actually thrown up. I’ve always just felt like it.