How can I save my little tree?

I am not sure of the variety, but it is a small tree, possibly a shrub. I'm pretty sure it is a gardenia. Right now (and when I purchased it) it is about 4 feet tall, with the trunk about 2 feet tall. The leafy part is about 1 1/2 feet tall and about 2 feet wide. I bought it from Home Depot in February of this year, and it has not bloomed at all. For a while, there were a lot of buds on it, but none of them opened up. They just turned brown and fell off. Now the leaves are starting to turn yellow, and I'm sure it's not because of over-watering, as we have been dry for a while, watering scarcely. We planted it directly outside our front door (east-facing), and I think the problem may be too much sun. I am considering replanting it, but I don't want to stress it more as it appears to be very fragile right now. I live in Southern Florida. Any ideas would be appreciated!