Bleeding at 12 weeks

I think I’m mostly just looking for some reassurance. I woke up this morning to some bright red bleeding. No clots, still just normal round ligament cramping. Called my OB, went to the ER, had a small bedside sonogram done and baby looks great. The ER doctor suspects that it is a subchorionic hemorrhage, but didn’t want to dig too far into it since baby looked good and I have an appointment with my OB tomorrow. I’m just having small amounts of dark brown bleeding now. And not heavy enough to show up on a liner. Only when I go to the bathroom. Has anyone else had this happen this late in the 1st trimester? I guess my biggest concern is that I have had 2 ultrasounds previously and a hemorrhage hasn’t been noticed before.