Just wondering,

Ok so I'm on like a 45 day or so cycle, my last AF started on the 28th of march, but I've been having really strange sensations, I feel what seems to be kicks, I have nausea heart burn, pee a lot, hot flashes headaches, stuffed up..etc, and I know its too soon since last AF to even possibly be pregnant, plus i freaked myself out and actually took one, negative...I don't understand what's going on, Dr doesn't have an explanation either... I've heard stories of women having pregnancies that only showed positives on the blood work, no urine positives...I don't know what the hell is going on, anyone else ever have this happen? Just would like to know I'm not alone and if anyone else has experienced this, what was the diagnosis if there was one?