Random question

Adele ā€¢ PCOS Baby dust to everyone!! šŸ™šŸ»šŸ™šŸ»
So I'm 20 years old I am currently ttc and I was just wondering and it's kinda dumb but I've heard of it happening so no rude comments please. I took a pregnancy test last month because my cycle was 54 days but I took it BFN got my period but my stomach looks big like bloated and everyone keeps asking me if I'm pregnant. Was wondering if there us anyway I can be pregnant but it would show up as negative. Please answer to the best of your ability thank you.