Ok, so its been about a week 1/2 since the sex. But for about a week, I've been feeling very different. Ive been nauseous, extremely tired all the time, even after 10 hours sleep, I have very tender breasts, and my nipples look a bit bigger and darker, and have little bumps around them. Ive been having some cramps, head aches and back aches. Im a little sensitive to smells, I can only eat top raman, and I was reading what a doctor of biology had said about implantation and how you may get a mild fever during it, and as I was reading it, I did have a mild fever. I even had heartburn a couple times, which I haven't had in years.
Also, I was ovulating during the sex. I did use a spemicide but I looked on the box, and it said it had expired that month, and it was the end of the month. Im sppose to start my period in a few days. So I wasn't sure if these were just weird period symptoms that I've never had before, or am I pregnant?
Im only 18, I'm very nervous. So if you can just tell me what you think it would be great. Thanks:)

It's unlikely but not impossible that you'd be having all those symptoms this early in a pregnancy... most of the ones you described show up later in the first trimester at the earliest. Still, because it's not impossible, I'd strongly recommend at least a home pregnancy test, if not a trip to planned parenthood if you don't start your period on time. Also... maybe start a multivitamin regiment now and pay attention to the nutrition of what you're eating... just in case...