I've just noticed this over the last couple of weeks - quite a pronounced soft fleshy bulge when standing. I had quite a bad separation of my tummy muscles after dc1, but lots of physio and managed to get it back pretty close (have had 2 more dc since with no problems). Have tried having a feel when lying down and it still feels quite close together when I tense the muscles.
I recently started training for a marathon which is involving lots of hard surface running - that's the only difference I can think of recently. I'm not overweight and pretty fit. It doesn't hurt. Could it be a hernia?