Help?!

So my boyfriend and I have been ttc for almost 2 years now and I have irregular period so I got this app to help track it so we would have a better chance but this time I am 16 days late. So I haven’t had a period in 55 days. I have been showing some symptoms of being pregnant like nausea right when I wake up or about an hour before I go to bed, my lower back has also been hurting, I have been more tired than usual, urinating more frequently, and my breast and nipples have been sore but when I took a pregnancy test the other day it came up negative. Do guys have any insight to what might be going on??