I had unprotected sex 12 days ago. The past couple days I've felt like my period was coming, but it's now 2 days late. Frequent mild headaches, lower back aches, slight cramps, dizziness, tired, just don't feel right, want salty soup all the time, thirsty, feel sick every once in awhile, usually when I first wake up and I'm hungry. Normally my cycles are about 25 days. I took a test and it was negative. Did I test too early or is my cycle changing for some reason?