am I wrong for being mad?

So me and my boyfriend have been planning to move out for a year now since we still live with our parents.  we had planned to move out once we got our tax return. we let his parents know since last year. Now we keep arguing because his mom came at us that we have to give her 5 to 6 months so she can save up money to move out and get a smaller apartment. Am I wrong for being so upset I feel like he left me hanging since I have to leave my parents house by the end of next month? I feel like he needs to stand up to his mom and tell her something. I had told him to just give her some money. Am I over reacting I feel hurt. I have no one to talk to about this.