Bleeding/Spotting

Hey!

I’m about 15 weeks pregnant. Had bleeding at 11.5 weeks and again at 14 weeks. I’ve had multiple ultrasounds and everything is fine. My cervix isn’t opening. But there’s no explanation as to why it’s happening. I have noticed it’s when I’m walking a lot or doing a lot during the day or day before. I’ve also noticed it coincides when I hold my bladder for too long. I can’t say it’s related but it’s the only thing that’s consistent. Has anyone else had unexplained bleeding/spotting? My doctors don’t have answers and I just want to know why it’s happening.