Why am I feeling like this??

Okay, so I am light headed, my lower back aches A LOT (Mostly one side right now) accompanied by cramping. I have a horrible head ache, I am feeling very tired and somewhat nausious. I have also been pretty emotional lately. Can anyone give me any clue what is happening with me and why they think so? Looking back at this, it may sound like pregnancy but I did have my monthly on time and it isn't due for another few weeks. Could Pregnancy be a possibility at this point? What other illnesses may these sympotoms relate to?Why am I feeling like this??
I'd say really early pms maybe. or mono could explain the back ache, head ache, and light headedness, have you checked to see if you have a fever? either way I'd say go to a doctor, they'll know more than people on the internet
Maybe it has something to do with your diet- are you eating enough?
Do you have a bladder infection?
Pregnancy is possible if you've had sex.