Weird Period.

So, for a week or so before my period I was very nauseous. Especially when I ate. One day I started cramping pretty bad, normally with my periods I bleed THEN I cramp. That wasn't the case with this one. All day I kept checking to make sure if I started or not, there wasn't any blood. I get home and I use the restroom, all of a sudden it was like brown stuff with a tad bit of blood. I was worried because this isn't normal for me. All night I kept checking and checking. There was more and more brown stuff as time went by. I was heading to bed so I put a tampon in. When I woke up it was full with blood. So I started. My period only lasted about 3 days. It ended yesterday very suddenly. I woke up yesterday with a lot of blood, then last night there wasn't any at all. Today there hasn't been anything either. But what's weird is I wok up last night and felt like I was going to vomit for about 2 hours. I was very light headed, hot, and sitting by the toilet. I didn't vomit, it was just a very bad feeling of it. I woke up this morning and I still feel very nauseous. I don't know what's going on, and quite frankly it's freaking me out. Could I be pregnant?