hi, 2 weeks ago, i started to feel cramping like i was going to start my period, but it doesnt start until the 20 of dec. than week after that, my breasts started to hurt really bad. and the cramping stayed the same. now, my period started a week early, only lasted 2 days and now its light brown. but my breasts dont hurt anymore, but now my cramping is still there, but very mild, and now my lower back hurts and im tired at odd times during the day. last week i took a blood test and it came out negative. do you think i took it too early? what does this mean?