How do I know if I had a chemical pregnancy?

I took 2 pregnancy test like last week and they both came out positive and then a few days after that I took another one, different brand and it was negative. I then got my period on September 11th.. I heard that if you take a test and it says positive, then negative and you end up getting your period, it was a chemical. And that's exactly what happened to me.. :( is there any way to tell or do I have to go to the doctors?