Hi Mel,
This happened to me around 10 weeks. I would get a heavy type feeling, just above my pevic bone, then I would get slight bleeding... Sometimes, the pink stained CM would be there without the heavy feeling. This went on for 3 days and I freaked out. My Dr referred me for an ultrasound just to be on the safe side... and bubs was fine, and no cause of bleeding could be found. I was also tested for UTI, but that was all clear too. It was put down to being a slight breakthrough of AF.
If you're concerned, give your Dr or Midwife a call and see what they think.
HTH
Lisa