I asked the same thing at around the same stage. I didnt have BH with DD but my midwife reckoned that it wasnt BH but that woman are more 'sensitive' at certain gestations and things like that can be felt more easily. Who knows if she's right, but at 12ish & 16 weeks I would get a tightening across my tummy and then a little hard 'ball' area which I assume was baby.