Pregnancy test negative....

So me and my wife are trying to get pregnant. We did donor insemination on the 15th of Dec. I was at my high point for getting pregnant on the 15th and the 16th. I have taken 2 test one on Christmas day (early i know but you know wishful thinking) it showed negative. So i took another one today around 4pm just to check again and it showed negative too. My period is in 4 days and im 30 years old btw. My symptoms so far have been peeing a lot more than normal, eating more than i usually do, nausea but not getting sick and im always thirsty. So my question is.... Is there anyway that my HCG levels are still to low for the test read or is just negative because im not pregnant?? Or has anyone ran in to this before???