Flowers dropping off- help please

[love2travel]

Hi everyone, I am new to the forum and new to having ever owned an Orchid.

I bought a Cambria spider orchid from my local garden centre at easter, and now the flowers are all falling off. It is in a china pot with no other pot inside, I was worried about over watering so have only watered it once since easter, and it was after that the flowers started to fall off. Although I did move it to another place in the house and then back again.
I went back to the garden centre and spoke to their plant expert yesterday, he said I hadn't watered it enough, he told me to repot in a plastic see through pot, to water once a week by standing it in tepid water for a while and to feed it. I have watered and fed it, with a feed that you stick in the pot, but haven't yet repotted it, as I am not sure what to medium to buy to pot it with as the only plastic pot size I saw was a bit bigger than its in now, more flowers had fallen this morning.
Please can someone help, as I would prefer the knowledge of people that know about orchids.

I have just noticed that all the flowers that have dropped off have come off the same stem the other stem seems to not have lost any flowers?

Thanks in advance.