Harry is 6 months old today and he has a very annoying habit i need help with......

when we brought Harry home i let him sleep on my bed, this was fine as he was housetrained, then all of a sudden 2 months ago he started weeing on the bed, apart from this habit he is perfect in the house, clean in his own bed but he is still weeing on the beds

Now Harry sleeps in the kitchen, which i hate, but i can't afford to keep buying 2/3 duvets a week!!

how can i get him to stop???