Getting confused

Well if you didn't get to see my last post, I posted about how me and my husband are trying to get pregnant with baby #3 and I had a very light period that only lasted for 3 days. That is abnormal because my periods have been heavy since I was 10 and I'm 24 now and they always lasted atleast 5 days. I took 2 pregnancy tests and they both said negative, I took one at night and one in the morning. I just thought 'well maybe I didn't wait long enough so I waited about a week and a half and bought 2 more and both of those said negative. Is this a sign that I'm not pregnant and need to keep trying or is there a such thing as a false negative test? I feel like I'm pregnant but I'm not sure if maybe that's just my mind wanting to be pregnant. Everytime my husband and I do the deed it's uncovered so I'm hoping if I'm not pregnant that soon I will be. Any advice or guidance would be greatly appreciated :)