What do you guys think?

So since trying to conceive I have had two previous times when I was late, sick, but tested negative. After a few days I would have a period. So this time same thing sick when I'm suppose to be having a period and testing negative. Only this time I'm over a week late! Do you guys think previously I may have conceived but was chemically miscarried. Nausea and vomiting are not symptoms of my cycle. Any other time I just have some cramping and it starts. What do you guys think??