Spotting 13 weeks 😭

Kira • TTC 1st for 15mons and I finally had my BFP!

When should I be concerned and call my obgyn? I haven’t spotted since I was 7-8 weeks. I went to the bathroom and there was a little brown on my underwear and a little when I wiped. I see my obgyn next Monday, but I can’t help but be worried 🤦🏻‍♀️