Basically a Muslim should ignore doubts altogether and should make wudu’ normally one time, paying no attention whatsoever to the wasawis (doubts). He should spare no efforts to do wudu easily and without excess. After that, go ahead to offer the Prayer.
Attending more to the topic, the fiqhi ruling is to pay no attention to these doubts or wasawis and to go on with normal wudu’, salah, ghusl, etc. and worry not about that.

So, the first thing we advise is to ignore these doubts altogether and not to pay attention to them.

The second thing is to seek treatment on the hands of a trustworthy and reliable psychiatrist, preferably a Muslim one so that he would be able to understand and deal with it. Through our work, we encountered persons who experienced such disorders, but they visited a psychiatrist and followed his instructions until Allah granted them cure and health. Actually, the Prophet (peace and blessings be upon him) ordered us to seek therapy and treatment. Imam Ahmad reported that the Prophet (peace and blessings be upon him) said “Seek medication, O slaves of Allah, for Allah has not caused any illness but provided a medicine for it except one illness i.e. old age”

Further, the questioner should be assured that the suffering he is experiencing is a test from Allah, and that his patience will be of great reward. The prophet (peace and blessings be upon him) said, “No fatigue, nor disease, nor anxiety, nor sadness, nor hurt, nor distress befalls a Muslim, even if it were the prick he receives from a thorn, but that Allah expiates some of his sins for that.”

Finally, and most importantly, the questioner should seek Allah’s help and support, asking Him Almighty to heal and comfort him. He should try to strengthen his relation with Him Almighty, adhering to His commands, and refraining from His prohibitions. In any problem, Muslim should resort immediately to Allah, for He, and He alone, can cure the patient and relieve the distressed. Be confident that He Almighty is the All-Merciful and that if you return to Him He will not let him down.

May Allah guide all of us to what pleases Him!