I think you can feel cramps or twinges a lot of the time as your uterus expands. I felt cramps right at the start, and I've felt them at times, more through a bit of constipation, but I have had major 'twinges' (not that I'd call them twinges!) at times. If in doubt, check with your GP but if a comfortable position or a lie in the bath eases things then it's probably just down to your body changing inside.