Ok; so my parents have been married for about 18 years. My family was always like a loving close family, but once my mom found out my dada was cheating, they fixed everything and my dad stayed because my mom begged.
A few months ago I started to think that my mom was now cheating because she would go out almost everyday she would look so pretty, even prettier then going to a party, then come all messed up. I once heard her blow kisses to a someone on the phone, and sweet talk to someone and she talks on the phone almost all the time, but idoubt it was my dad because their relationship isn't the greatest.
Recently ifound a picture of a guy between her belongings , idont know who the guy is but I scaned his picture to my computer just in case.
My dad is always working and he never has time for anyone not even himselve so he probably doesn't realize this, but I have I notice everything happening, now I don't know what to do, should I tell my dad what I have seen and heard? Or should I stay quiet, should I tell mom what I have seen and heard and let her explain? Or what should I do?

By the way I am 14 years old.
& who ever wants to reply mean things I suggest don't even bother posting it please