15 days late on period too early for a pregnancy test?

So I'm 15 days late on my period, and it's usually pretty regular. I've taken 3 tests but they've all come back negative. And yet, I'm still having all of these symptoms that are common for pregnancy. I'm super concerned because I have a non hormonal IUD, and I don't want to miscarry. Based off of the most likely date of conception, I would be about 6 weeks pregnant and the longer I keep my IUD in, the higher the risk. I'm just curious as to if anyone else has had issues with home pregnancy tests showing false negatives and if it's just too early for it to show up in my urine. This is my first possible pregnancy so I have so many questions