unreliable Fiance

My car needs a couple of repairs before the inspection due in 3 weeks. My fiance has been putting it off or forgetting to fix. Now he tells me he doesn't know if he can fix it, which is a total lie, he's not bothering to help me out. Sending it to the mechanic means would be out of budget. I'm saving up to buy a new one by the end of the year. I'm now really angry and disappointed at him for not being reliable and it sort of makes me question if I can rely on him when I need him like now in the future.

Am I overreacting or is this a good reason?