Very Curious

I usually have irregular periods so I never notice when I'm actually late. 

I started cramping badly about a week and a half later. I also spotted one time about a week and a half after having sex. I took an at home pregnancy test (in the afternoon) at the exact two week mark after sex and it was positive. I took another test the next day (in the afternoon) and it was also positive. I took one more test the next morning (so now two weeks and three days after sex) and it was negative. Very confused. I've been cramping everyday since. My cramps are about once every hour or couple of hours. I had lower back pain for two days but that's all. 

No sore breasts and no more spotting. Only cramps. 

I'm curious of the different opinions about what's going on. Any advice or suggestions? 

Thanks