is it me?

So I am in a hetro relationship after my wife of 14 years cheated on me. we are seperated and working on the divorce.

my boyfriend 33yrs old cant keep it up! he can get it hard but once we start having sex it goes flacid. he swears it isnt me but I cant help but wonder. i have had a child, does that make you loose? I am sexually frustrated and feeling really low about myself.