I'm starting to lose it at this point. I had sex with someone a few times in early June. I experienced horrific cramps in the middle of the month with nausea and dizziness. Then the heartburn arrived a few days later. My period arrived on July 2nd and it was light and only lasted 3 days. The nausea, heartburn, dizziness, and exhaustion continue even though the urine pregnancy tests still say negative. Is it possible that I'm not pregnant and this is all in my head?