you might be bloated form the missed periods??? I was the same, regular like clockwork except for one time when I broke up with my boyfriend at the time and I was 3 weeks late. I miss a period when I'm stressed. I'd get the ultrasound if I could. The stick tests always came back negative (even when I was pregnant) but he blood tests were right. But they can always make a mistake in the lab. Good luck, it does sound really frustrating!!!!