I know the feeling. Life can be hectic when you least expect it, especially with renovations on a house. However, ask yourself these questions:
1. Are you done renovating the house?
2. I know I plan on this costume for Halloween, but can the project be saved and on time for a convention?
3. Do I have the weekends off?
You answered all these 3 questions yes, then all you need to do is take the weekends that you're not working full-time and the time you used on renovating the house on for the construction of the costume. If you answered 2 out of the 3 questions yes, then make a plan on when would be a good time to get back on it before Halloween comes around. When you go by that said plan and when you start back working on it, you'll get your motivation back.
I've made up that plan for myself because I know I'll be getting my art website up and running soon. So I plan my cosplay constructions on the weekends and work on my artwork (as my career) on the weekdays.
If worse comes to worse that if the costume somehow didn't make the Halloween deadline, but you know what you need to get done and what you have done on the costume, then you'll know that it can be used for the next convention