I had AF type cramps for two weeks along with extremely sore breast. My period was 6 days late, back pain, headaches, dizziness, extreme tiredness, OMG ready to scream at everyone. So after day 7 with no AF I decided to test after work. (In theory, if I was Prego it would show up no matter what since I was six days late.) The test was positive and just to make sure I downed more gatorade, went to the drug store and bought another sure enough it was positive.
The bad thing for me, was I had been TTC for a while and was having alot of the symptoms I would get before my period would come so every month I thought I was pregnant and wasn't. That's why I didn't bother testing for so long.