Light red and brown discharge during time of period. What is it?

[Unknown1227]

Okay so. I'm supposed to be on my period this week. My period is late but my "CLUE" calendar says I was supposed to have started yesterday. July28th but on July 27th after sex I went to the restroom and when I wiped there was a little bit of light red blood (pink) also it was no where enough to be even close to filling up a small liner. So assuming it was my period I placed in a tampon the next day 28th the day of my start day. My tampon was empty, and no color when I whipped. Now today it was the same thing. No color clean tampon up until about lunch time when the pink came back (still not enough to fill up a small liner, not even close) with some light brown blood that I usually get when my period has ended. The past few days prior to my "starting period" I've thrown up but because I'm not the type of person to actually throw up I've just been throwing up in my mouth. (I know eww) it's just a little bit of throw up not a lot. and it only happened 3 times. I have had un protected sex 7 times this month and I am not on any sort of birth control or taking any medication. Could I be pregnant? Or just a crazy period? Or should I just wait it out?