Is this his first child? he probably got scared thinking if he be with you he has to provide for 6 himself.
don't forget family & friends play a role in this. he might've had a few people come to him and tell him not to be with you b/c he would have to be responsible for 5 kids.
My best friend has 5 kids & married, but she had to endure people telling her now husband not to marry her b/c she has 2 kids not his.
but i m surprised about the lack of interest he shows in your pregnancy. this tells you what kind of person he is.
don't feel like no man will ever love you b/c of your kids. i think you shouldn't even worry about your ex right now and focus on your kids. the more kids you have the greater the chance one of them will help you when your older. but concentrate on your family and forget about that looser.
what are your children ages? do you have other kids in diapers?