Can you have gotten your period, and had an at-home pregnancy test be negative, but really be pregnant?

I’m kinda worried because my friend’s mom didn’t know she was pregnant until she was almost in her 3rd trimester because she kept getting her period and just thought it was a stomach tumor. But for over a month now I’ve been feeling kinda hormonal mood-wise and my breasts are really tender and I’ve been more sensitive to bad smells, even having them make me puke a couple times. So I’m totally freaking out. Can I possibly be pregnant? Or is there something else going on?