What is this 😱

So I was supposed to start my period three days ago. And the first day I cramped really bad like I was going to but all I did was spot I never really “started. Today I went to the bathroom and seen this on my underwear. It doesn’t look like it in the pictures but it was all kinda wet and gooey and brown. Does anyone know what this could be or could someone help me figure out what it is?