chemical pregnancy? or not?

I'm so confused.. aggravated.. mad at the world.. back in may I had what I would assume to be a chemical pregnancy. Four different tests all taken on different days all saying positively pregnant. I was two weeks late at the time, and boy was I excited ! I made my first appointment for when I'd be 9 weeks, about 5 days passed and I have my world turned upside down. I went to work, feeling sick to my stomach thinking "oh this must be morning sickness starting early".. but no. I go to the bathroom and it's a blood bath. I went to th hospital, they did no ultra sound just blood work and simply told me "you are not pregnant" and your levels were so low that you may have never been. I can't get it out of my head. I have so many questions that they just were not concerned with. And now I'm left wondering what happened. How could four tests be wrong ? My mind just can't rap around all this. It has me sick. And now my husband wants to try again or try in general. We've been trying. And nothing. I have two other children so it's not that I can't have kids. I'm only 25 so I'm in my prime. I just don't understand.