Could I be?

Okay, so I am 20 years old and me and my boyfriend (who's 26) have been dating for about 6 months. We've been having sex from pretty much the start. At first we used condoms for the first two months, but then we stopped because neither of us liked them. Then he pulled out, but for the last month and a half hes just been cumming inside me. (I am not on the pill or anything) I had my last period March 14-17 and am not due again until April 11th so I have another 6 days until it's due but I am scared I am pregnant. I am usually always tired but lately I've been way more tired and always seem to fall asleep super early, and sleep in super late if I don't have to work. Two weeks ago I was sick to my stomach every day and even threw up a couple of times but I haven't really had any stomach aches since. Also my back's been hurting which is really weird because it's never done that before. I don't know if its because of my new job or what but I've never had back pain before. I've also been peeing a lot lately, and I have a really bad headache every day. And I've been eating way more then usually.

All of this could be in my head, but I want to know what you guys think. My boyfriend said we shouldn't worry about it until I actually miss my period but that doesn't mean I am not.