Confused

Reina

So I had my period really short this month (only 2 days of spotting) and this app says I'm fertile this week but I been cramping all day a lot so I went to the restroom because I feel really bloated and all so I wiped and it was light brown. So what does that mean? I took a test 2 days ago and it was negative. Supposed to start my period again Dec 4th.

Please help? Thanks.