Camellia problems.

Hi,could anyone please give me some advice on my potted Camellia, as I am not very knowledgable about these plants,I had this one bought for me about two & half years ago.It only flowers from the middle,downwards,anything above is just leaf growth,the leaves are still budding but wasn’t any flower buds.Also the leaves are turning blotchy & yellow.I just don’t know whether  to prune it down to the middle after flowering or leave it as it is.It is planted in Ericaceous compost.Any advice,gratefully received,thank you.