DAMP SMELL IN HOUSE HELP

[tabbycats]

Hi,
We moved into a rented 4 bed house in june which prior to us had been lived in. The smell of damp in the living and frontroom areas are very strong, also we have damp smells in the kitchen. the landlord has had our carpets cleaned and supplied a humidifer but the smell is still there, i open the windows daily .
Recently i found mould all over our clothes in the upstairs bedrooms. The landlord just suggested to get a cleaner in which we did who said our house was clean, and this was not the problem.
The house is brick has had an conservary built on the back, it also has 2 pounds in the front garden?
I am unsure what to do next i have approached the landlord and gone with all their ideas, but the smell is strong. I have a 1yr old and it worries me he may get ill.
Could you please advise of any ideas am at yt wits end
Thank you

[welsh brickie]

Are the ground floors wooden??If they are, I suggest having a look in the floor void beneath it could be that.
Also do you suffer from condensation problems on the windows.