Hi Ozziehoffy
Without getting more info I cannot be 100% sure but I think that it is either:-
The stretching of your ligaments/muscles
Or
Your pubic bone. During your pregnancy your body produces a hormone called relaxin. This hormone causes all your joints and ligaments to relax. Your pubic bone has a joint in the centre of it which does not normally move. However, for some women, this joint can become loose under the influence of relaxin. When this happens the edges of the joint rub together causing pain. The pain is usually a sharp stabbing type pain and happens more often when you or your baby moves.
I don’t think that your pain is related to your CS scar.