I Have Von Willabrands Disease. I Was 13 Days Late

I have von willabrands disease. I was 13 days late on my period last month so took a pregnancy test it was a negative. Then a few days later I started to bleed, only bled for one day then stopped for a day then started bleeding again for 3 days. During this I had terrible cramping before and during and after. I then took a pregnancy test after i stopped bleeding and got a faint positive result. Could I be having a chemical pregnancy?