If you're already pregnant, then the decision to have the baby is completely yours. But you need to seriously consider what he's saying while you make your decision. An unwilling father can make your life miserable. Even if you manage to get financial support from him, you can't force him to be a father. And he can also insist on custody/visitation rights even when you are not together and you will have to share birthdays/holidays with him. And most unwilling fathers skip out on the child support even after its court ordered.
As far as your mom, well its great that she's offered to support you. But you need to plan as if its only going to be YOU there for the baby. Because thats all you can really ever count on. Your mom says she will help now, but things happen and she may not be able to be as much help as you need. Daycare is expensive and if you don't have a good job, its not worth it to work to pay daycare. Your mom has her own life I'm sure and could have health issues later that prevent her from being helpful.
If you're not pregnant, then DO NOT get pregnant to try and manipulate your boyfriend into something he's not ready for.
Wait until you find the relationship where you both want the same things out of life. If its not this one, then there's always others.
Men are like buses...if you miss this one, there's always another one getting ready to pull through. :)
Good Luck!