Help please!!

I have been having brown discharge since last night when I wipe. It looks like discharge I used to get before my period. I have had some lower back pain today with mild cramping. When I went to the bathroom earlier I passed what looked like a light brown clot. Has this happened to anyone before and they were ok? I had a scan 3 days ago and baby looked great, I'm just worried. I'm 12 weeks 2 days