Wierd Period? or Pregnancy?...Anyone Been through this?

Ok, so, I had unprotected on the Nov. 4th (pull out method)...no lectures please...Anyway a couple of weeks after that i started feeling fatigue, lower back ache, a little nausea (no vomiting) here and there, emotional, felt like i could never get full.(i would literally eat a big meal and an hour later be starving)...so i suspected pregnancy. Well, my period was due on the 25th, but it came on the 23rd...and it was wierd. it wasnt my normal light to heavy to light..it was like spotty..then kinda flowy but not really, then light, then 2 days later it turned brown and dissapeared. My periods are normal like clockwork & always last 6-7 days, this is the first time its ever been this short. Now that its gone i still have that "feeling" like im on my period..I took 2 prg tests last week and they both came back negative. I have a docs appt for a blood test in 2 weeks, but until then just wanted 2 get some input, has anyone been thru anything similar? Thanks, serious answers only please