messaging bfs ex girlfriend...

hello ladies before I do this I would like to know some opinions on weather or not if I should message his ex girlfriend.... here are the reasons why I want to message her... I want some type of closure or advice or some knowledge as to why my bf is acting they way he is ( feels and seems like he's cheating) I want to ask her if he wasn't touchy feely with her, if he cheated on her and if he never put any time or effort into her as well because I feel like it's all my fault and messaging her I feel like would help me out... yes I know him and I shouldn't be together if it has to come down to this but I just want to message her to see what she says.... do you think I should or not?