M.W.
Wow this is tough!
A few things jump out at me..
1. You don't have to have money to get married, you could have a small simple wedding on your own dime, what makes it special is the people there, not the amount spent. So if Mom is overreacting and trying to control him by withdrawing the funding for this wedding, you could proceed anyway. HOWEVER...
2. Why is she doing this? If she has some concerns about him, say his moral character, or if he's going to be able to financially support you, or some major concern like that, you should listen to her. When we're in love we are often blinded and miss some obvious signs that someone isn't a good person to marry. Listen to your mom if she has a legitimate concern about this marriage. She wants what's best for you. Having a baby with someone is NOT a good reason to get married. They can still be in the child's life, especially if you choose to get along with them and make it possible, but you shouldn't marry for that reason - I've seen too many marriages that use children for glue to hold them together. It doesn't work, it just destroys the child.
3. Time. Time heals wounds. What's the rush? Getting married before the baby is born isn't going to matter in the long run. If you can get some reconciliation between your man and Mom, then its worth the wait because you do marry each other's families. If this is a petty issue, they need to grow up and make up. You should be frank with them both that this quarrel is greatly disturbing and they need to make up and move on. It would be much better to have the issues resolved and a marriage that the whole family is happy about then bitter feelings. Both of them are important in your life.
Best wishes!