What is this?

Before you look, excuse my stretch marks and hairs. Ok, what is this line running up my belly? It has not been there before and I’m 100% sure of it, am i tripping or is this the línea nigra? I’m supposed to start my period later this week and I’m super bloated and have been cramping like usual, but then this morning i see this. Is there any other reason for this line besides pregnancy? Could this be part of my period symptoms or is a line like this a definite pregnancy? And if I were to be pregnant the lastest I would be would be about 4 weeks, wouldn’t that be to

o early for a line to show?

Thank you guys for the responses! I guess this isn’t abnormal and I should be expecting my period on regular schedule lol