what is this?

so I haven't started my period yet (I think im a month late , haven't really kept track of it) , but a couple days ago I had maybe 4 cramps in ten minutes , and I thought I was about to start so u put in a tampon. I checked and it was covered in this brown stuff. and the time I've ever seen this is if I would leave a tampon in to long. but there was a tiny spot of blood. done it again today and the same thing happened. I checked myself and there was no blood there just brown gooy stuff(again as if you leave a tampon in to long) I don't know what this is , its never happened before. I'm not sexually active either. should I be worried? what is it?