help!

[sweetgirl27]

My last period was September 13th, 2012, and ended on the 17th of the same month.
I had unprotected sex, stupid yes, I am aware, with someone who I am not in a relationship with, on the 28th of Sept.  I went to look at an ovulation calculator just to see how things go during ovulation because Its been awhile since I had an anatomy class.  But the calendar said that the best day of my ovulation to have sex was between the 27th-31st.   Not to mention it just so happen to be right in the middle of my cycle (25-28 days) and I've heard that during that time is the best time to get pregnant.  

The calendar/calculator also had that my implanation day (if I were to be pregnant) would be today, plus or minus three days.  Well, when I woke up this morning I had an incredible lower abdomen pain on both sides and then I felt it in my uterus..kinda like a period cramp, but far worse. Since then I have noticed a light brown discharge...I'm a little nervous..but any feedback you guys can give would be great.  Thanks for your help!

[sweetgirl27]

I've also for the past two days been experiencing tear jerking back aches. It seriously feels like my back is stretching side to side.  Does that make sense? Any input about it?? Thanks so much!

[naan84]

its very possible if you had unprotected sex during your fertile days. best thing to do i take a home test or go to a doctor for a blood test. if testing at home wait a few more days, if you test too soon you may not get an accurate answer. the best time to test is after a missed period. a blood test will give you the most accurate and fastest answer.