son's father being in and out of his life

my son is almost 8 months old.. his "father" hasnt seen him in FOUR MONTHS and hasnt even attempted to contact me in two months, until recently

. that's not the first time he's been out of his life either. when he was first born, he saw him a few times, then didnt see him again for weeks.. he's only seen him less than 20 times in the 8 months since he's been born. every single time, he comes back with an "im sorry" thinking it just makes everything better. before, i wanted him to be in his life SO BAD and it broke my heart that he didn't care, but now, for the sake of my son, im just over the entire thing. i dont want someone who isn't going to be consistent ruining my son's life.... but i honestly dont want to make the wrong decision, so im very unsure of how to handle it.