@Oct18thlove,
Well, in any case I think you're answering your own question. You asked "why is he a flake?"
Well, without knowing the man but based on what you're saying here it is quite obvious, HE IS IRRESPONSIBLE! The fact that he cannot do basic communication with you like a text or what-not demonstrates his unwillingness to communicate and I wouldn't be surprised if he becomes uninvolved in this child's life after it's born.
I also think you made a poor choice in picking a mate and grant it nobody knows the hands we are delt, but it seems that this guy was not a suitable partner for you. My best advice to you is stop worrying because your main focus ought to be on the baby and not wonder about why he is flaking. Let him contact you and when he does, the basis of your discussion should be about what you both are going to do about the baby.
If he continues to flake, child support will make sure he wont flake!