Did you have your blood drawn for the test at the same local lab each time? Do you think there was any error in handling it? Can you tell the names of the companies that processed each DNA test? (In your prior post, one of the people responded as though she heard you say the DDC processed one of the tests.)
Or were all three tests done by Ravgen, in Virginia? It is a top lab and it would be surprising if they would just shrug their shoulders and give up.
You say you "keep" wasting your money, but if the lab you're using is Ravgen, it would also be surprising if they would charge you more than once if the test was simply too early. I think they would simply ask you to wait until more DNA is available in your bloodstream from the baby, and then they would have you test again. I don't think there is a charge for this.
Another reason there might be not enough material from the baby in your bloodstream is if it has stopped developing. Have you had an ultrasound recently? And the baby is growing at the rate expected?
Don't know what else to suggest, except to say that by your 12th week there should be enough material from the baby in your bloodstream for the lab to find it.