I've been feeling like this for a long time now, though for different reasons.
I have a hard time enjoying anything, therefore I have a hard time caring about anything enough to wan to learn about it, do it, talk about it, or even think about it, therefore I have a hard time making conversation and connecting with people.
I feel this way because ultimately I fear I'm incapable of meaningful significant achievement due to lacking genetic talent, as evidenced by feeling like I'm not good at anything right away, and I thought that if you were capable of something, you would know it because you would be good at something right away.
Therefore, I feel "meh" about everything, because I feel like nothing is "for me".
If I could only kick ass at something, especially something meaningful to me, I could escape despair.
For you, it sounds more like intense work burnout due to having to take on much more than one person should be reasonably expected to, and when you get home there's just not enough energy left to feel more than "meh" about anything.