We bought this plant about 2 weeks ago in almost its peak blossom. It's kept in the semi-bright living room with no direct sunlight. According to the caring card, it should be watered scarcely, i.e. when the soil feels kinda dry. I wastered it a few days after the purchase when I felt the soil wasn't moisture enough, well not too dry either I got to admit. But since then its leaves started turning yellow and falling off from the bottom part. I'm quite worried about whether it will survive too much longer. Can anyone please help me figure out what's happened and how to save it? Thanks very much in advance.

p.s. Im new to this and cannot see how to attach pics here to show it