My period was on April 4th. My bbt went from 97.75 on the 16th to 97.36 on the 17th back up to 97.62 on the 18th, 97.63 on the 19th. Then I ve had a headache since the 12th, now backaches, cramping, light headed and dizzy, I don t feel like I am pregnant but keep thinking that I am.