Anxiety disorder. Will really help me.

Sir, m going through a tough phase of my life, worry all the time thinking about all the things happened to me which might have been occurred yesterday or 1 or 2 years back, just constantly think and try to rectify things in my head like- i should have done like that or may be in some other way and this way just keep myself engages. It happens with all the future incidents as well which I am gonna face. Situation gets worse during my exam, my heart beats becomes so fast that I can't focus at all, perhaps in medical term it is called as panic attack. Sir, i have to appear for a typing test on 6th feb as its the last stage of getting a government job so m really worried about that. Prescribe me some medication which might turn things calm for atleast those 15 minutes of my exam. It will really help me. Thankyou.