Hello everyone. I'm wondering if I could get some advice on getting my Chinese Elm a little more "healthy." I've had this elm for about 4 year and I believe it's about 16 years old at this point. I believe when I got it the smaller branches had more leaves but they seem to have just disappeared over the few years. Sometimes they will bud there, but not often. I have slowly been losing leaves over say the last 6 months, more so in the colder weather.
The tree lives by a fairly thin drafty window most of the time. I have recently moved it to a table with a south facing window and farther from the window so that it doesn't get so cold. It's been indoors since I got it.
Honestly, I've never been that good at trying to shape the tree. I usually just leave it alone, water it 3-4 times a week, and prune it a bit when the growing branches get long. I'd probably prune back the long branches you see in the pictures to 3-4 leaves, if that makes sense at this point.
I don't think the tree is dying, but I'd like to get it more full. I also really don't know if it needs to be re-potted, etc. I've never done it, and am a little afraid of doing it now as I don't want to kill it. I've included a couple of pictures below. Any advice would be greatly appreciated.