I haven’t had my period for two months

The last day of my last period was December 16, 2019. Before then my periods would show up within a week of when I was supposed to get them. I’ve been nauseas, eating everything in sight, tired, I’ve had back pain, my breasts grew like an entire size BUT every single pregnancy test I take is negative. I’ve taken quite a few over the two months and they just don’t show positive but I’m not sure what else the signs could be