Facing problems in memorizing the things

I'm facing an issue of my memory , form past 2 months I'm unable to recall few things which I've already done,like I forget that I already had my lunch , I forget movie names which I've seen recently. Moreover , I'm having nerve pain in my body. Sometimes my hands veins starts stretching and that causes pain which is sometimes irresistible. I'm a smoker from past 5 years. But from past 2-3 months I've started smoking 5 cigarettes a day. I don't feel hungry , I eat so less and I feel so weak. What should be the mail reason for this? Do I have to worry about something ? Is my all problems related to my smoking? What should be done to detotixide my body if I'm a smoker? To which doctor should I consult for the solution of my problems? Lastly, I'm going for an interview on 2nd August for my army job and after that I'll undergo to a medical test. Will they be able to see that I'm a smoker ?