What you’re describing is time blindness, or a poor sense of the concept of time. It’s very common in individuals with ADHD. Ari Tuckman provides some great tips to manage it in this webinar replay:
Free Webinar Replay: It’s About Time: Understanding the Science of Time Management with ADHD
You’re also not alone in the hyperfocus and resulting exhaustion. Maybe try using your timer to allow you only a certain amount of time for physical tasks so you don’t get to the exhausted point.
Penny
ADDitude Community Moderator, Author & Trainer on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism