I pray to Allah to grant you success in your exams. I don't need to remind you about putting the best of your efforts while believing in Allah and in yourself to achieve success. You need to motivate yourself to focus single-mindedly on your studies; here are some du'as you may use:
Rabbi zidnee ilman wa fahman wa sidqan wa ikhlaasan wa eimaanan wa yaqeenan
My Lord, increase my knowledge and understanding; and grant me honesty, sincerity, faith and certainty of conviction.
Rabbi ishrah lee sadree wa yassir lee amree
My Lord, broaden my chest for me and make my task easy for me.
Allaahumma laa sahla illa maa ja'latuhu sahlan wa anta taj'alu al-hazana idhaa shi'ta sahlan
O Allah, nothing is easy unless you make it easy; you can make all difficult tasks easy; so make my task easy for me.
Hasbiya Allaah laa ilaaha illaahuwa alayhi tawakkaltuh wa huwa rabbu al-'arshi al-azheem
Allah is sufficient for me; there is no god beside Him; I place my trust in Him; He is the Lord of the Mighty Throne.
On empowerment and motivating yourself, you are advised to refer to the following answer.