YOu have a lousy relationship.
Why would you WANT to marry someone you're not happy with and who refuses to help with the children? Do you think marriage will solve any of your problems? Because the way I see it, it will only serve to padlock you to your problems legally.
You said that you are almost sure that he does not love you and that you are the one who is giving in and forgiving.
You said he refuses to help with HIS children.
You said you are not happy with him/the relationship.
What do you do?