Came back worse

So I was using a combination of a steroid gel and a moisturiser with added vitamin d for 1-2 months. I have psoriasis on my lower legs and ankles, which disappeared for around 4 or 5 months after treatment. But now it has come back worse, with tiny patches all over my forelegs and spreading to behind the knees. They are really itchy when uncovered, so like at bed time. I can't ignore the itching for very long as it causes a lot of pain. But even if I scratch them very lightly it feels like my skin is burning. Why have things suddenly gone worse.