Images are pixelated when transformed

Hello everyone, 

this is driving me nuts, I had no problems before, but when i transform any object it turns out a bit pixelated, ugly.. When I don't transform, it's all good... See example, the green thing is just right, but the image in blue is has all ugly edges, which I just rotated before... I think it's just an option i clicked wrong, but where, of what? Please help... 😕😕

Thank you so much for reading this, 

Kelly