I have felt similar to you. Our team goes out to lunch every few weeks together. My coworkers talk about activities that they do during the week...classes, sports, happy hour, movies, socializing. It makes me feel out of place. I don't seem to have anything to share with them because I tend to be too drained on most days to commit to activities. I can't remember the last movie I went to see. The weekends are usually better for me.