Mucus plug ?

tmp-9130512

This is baby number 3 for me ladies but my waters have Never broke by themselves and I've never lost my plug til in real labour ! I'm getting really bad tightening in my stomach an groin pain don't no if these are te start of my contractions or just pressure pain ! Does anyone no if it hurts or stings wen your loading your plug n some one put my mind at ease about these pains as I've never experienced these in my previous pregnancy ?? Thanks xx