Last weekend I transplanted it into a slightly larger pot with Miracle Grow organic potting soil. I also put one Jobe's citrus fertilizer stick broken in two pieces into the pot and watered it. It is inside in the sunniest spot I have. (4 hours of sun in winter) Because it's winter the sun is not as long as in the summer. The tree is only 18 inches high. It has two ripe lemons I just picked yesterday. It now has two lemons not ready to be picked, they're about 2.5 inches long. Until today it also had three tiny green lemons about a half inch each. They were all on a cluster. They fell off one by one starting two days ago, and now they're all off. Also, it started to produce buds this week before the green lemons fell off.
There are a variety of things that can explain why the plant dropped the green lemons. You brought the plant into your home from outside and the plant may have been chilled. The plant was repotted; the root ball may have been disturbed in the repotting process. The plant is growing in a new place and is adjusting to its new environment. Make sure that there is no draft in its new location and give it as much sun as you can. Do not fertilize for awhile and do not over water. That it is in bloom is a good sign