1. Try to communicate with them: discuss this issue frankly with them and see if they can share some medical expenses.
2. Seek legal help: If they are still unwilling to bear the cost, you can consider seeking legal help. According to the marriage law, children have the obligation to support their parents. If they don't fulfill their obligations, you can ask the court for help.
3. Seek community help: You can also seek the help of community organizations, who may provide some assistance or loans to help you bear the medical expenses.
No matter which way you take, please ensure your health and happiness. You may need to find a balanced way to take care of your father and your own economic and emotional needs.