Is the increased sickness of this young man who supplicates, "O Allah, cleanse my heart of doubts and desires," a trial to purify him from them?

There is no Shari (Islamic legal) evidence linking a man's supplication (du'a') to his frequent illnesses without a known cause. These illnesses might be a trial (bala') through which Allah expiates sins and elevates ranks, for a believer is afflicted with trials just as the wind sways crops, and trials continue to afflict believing men and women until they meet Allah without sin.