Update: still not doing well, has lost a lot of leaves. I don't know what else to do.

Lindsey, you might be overthinking this. Don't forget it's a little tree, and won't grow as lustily as a regular plant will. Btw, citrus do lose leaves all the time. They are evergreen so keep making new leaves and losing the old ones. As long as it has healthy leaves up top, you probably shouldn't worry about the loss of leaves lower down. The leaves I'm seeing all look good, shiny and a nice color. Just make sure it's getting maximum sun.

Did you pot up the plant yourself when you got it, or did it come in that pot? I'm just wondering if it might be worthwhile for you to slip it out of the pot gently and have a look at the roots. I would lay the pot on its side on some newspaper, and slide the whole root ball out. Take a picture and post it if you like. But if you detect a bad smell or see bugs or something, then some action might be in order.

Also, if you have a magnifying glass, take a close look at all the leaves and stems with it. Be sure to check the backs of the leaves as well as the trunk right down to soil level. There can be bugs that hide in plain sight, like scale insects that have a little shell over them and camp out on the stems. They just look like little bumps on the stem until you look closely. You can remove these with your fingernail if you see them. You're also looking for spider mites (although if you've been showering the plant regularly it's doubtful there would be any) or aphids which would appear on the tips of the stems, where the new growth is. I don't see any discolored leaves or signs of damage from insects, though. But I can't see as well as you can.

Thank you so much Elaine! You have been so extremely helpful. This weekend I will take the plant out and examine the roots and maybe do something about untangling the two from one another! It came in a smaller plastic pot and I transplanted it into this one!

Leaf drop. Whadda ya mean Texas has no humidity? 76* @ 4am and 84% as far north as Dallas. Not enough light!!! Must be outdoors. 60* is freezing for a lemon tree. There is citrus soil as well as citrus fertilizer, but the acid fertilizers for dogwoods and rhododendrons do fine. Don't be upset if you see no roots, mine has thrived for 7 yrs and I swear doesn't have a single new root. Moisture on a citrus can cause black soot fungus. Is there nowhere you can reintroduce it to sunshine? And fresh air?

I know you suffer with humidity in Texas just like we do here, but you do have more dry weather than we get in Florida, too. Lindsey lives in Ohio, so can't really plant a citrus tree outside. But I agree, it would be doing better if it could be out in the sun for at least the summer.

That black sooty mold is not caused by water on the leaves. If that were the case, every citrus tree in Florida would be black for most of the summer - it rains here sometimes every day for weeks. The sooty mold is caused by an insect infestation like aphids. They drop honeydew that stays on the leaf surface and the black sooty mold grows on that sticky, sweet stuff.

Lindsey, I'm wondering about the temperature in your room. You're probably running air conditioning right now, but if you're out during the day, any chance you can close your a/c vent to let it warm up in your room a bit? These trees do their major growing in the summertime when it's over 90deg. most days. Maybe your little tree thinks it's winter?

Thanks guys! I am going to buy a supplemental plant light. My boyfriends mom has one that is purely indoors and has grown HUGE. She has had it for years. My best friend also has one; his is little but has had a ton of blooms and lemons! Hopefully with more light and heat it will do better, my room can get a little cold from the A/C. Next month I move into my dorm and there is no A/C, so my lemon tree should love it! (Unlike me.) haha

Yeah, the aphids cause it, the shade doesnt help. Luck with the citrus

It's official... there were two trees in the pot! I took it back to the greenhouse and one of the experienced workers split the two for me and they are now in separate pots! Hopefully they do better.