Bra Problem (Nipple shows when I lean down)

I have a small issue that is really annoying. I have found a few bras that fit me me properly put some when I lean down if you look down my shirt (even T-shirt) you are able to see my nipple passed the bra. (If you look into the bra) The bra seems to fit fine but the motion of leaning down I guess presses the bra open specially if I lean down and grab something. Anyone have this problem? Is it the wrong tipe of bra I'm using? I've taken the maesurements many times and they fit properly. Is there a type of bra that doesn't open up like that when I lean down?