morning headache,nausea, fatigue, lowerback ache, weird feeling in lower abdomen

Hi, I'm 18 years old and my boyfriend have alot of unprotected sex like all the time. We even do it sometimes on my period. The last time I had my period was July 11. My period usually comes around the 9 or 10 and it hasn't come yet. And around the day I was supposed to get my period I was extremely tired. I came home from school and slept for like 5 hours straight. And then my lower back has a constant pain or pressure, the other day I was making a cheesesteak and I wanted some eggs so I combined the two and ate them. Then like 4 hours later I felt a little nauseous but didn't throw up. my stomach feels bloated all the time so I keep thinking that it's just my period coming but it hasnt yet. I just wanna know if I could be pregnant .