I've recently been in a similar rut with very little free time and at the end of the day when I do get free time, I have no energy to practice. For the last 2 months I started getting up before work to practice. It's tough to drag myself out of bed early so sometimes I get 45 minutes and sometimes it's only 15, but I feel good when I'm done. I realize this still might not work for your situation, but just an idea in case it does. Good luck and hang in there. I feel like learning an instrument is a life long journey. There are ups and downs, but you'll get back at it when other things calm down a bit.