I am a professional. I need to do lot of job in my work place, but I can not concentrate on one thing for long rather I roam around many things e.g. Some time I brouse internet, printing lot of documents from internet and try to read all but could not. I always change my mind. Some time I want to become great and after some time I feel very low in my mental state. I feel sometime that people are talking about my honesty, integrity and character. I can not remember a thing for a long time and often become confused with known subject. I possess very low self esteem and my confidence level is very low. I can become not successful in many work and jobs.

But I have a mind to do great in my area of interest. Sometime I feel interest in Physics, sometime in Mathematics, some time in GIS related field. But at last I could not maintain the continuity and all efforts become futile.

I can not express my opinion or thinking in a right manner rather in a fragmented fashion. I can not speak to a large audience, I becom feeble and my utterence become very short and not impressing.

Sometime I can not write any thing and when I start writing, the same word or same sentence recurrs. No more today. Any one there to help me out.

I think you need to practice. I've certainly gotten a lot better at giving talks with a few tries at it. For the first few talks you will need to do a lot of preparation, but you need to do less and less the more you do.

Spend some time thinking and talking to someone about physics or maths for 15 minutes or so a day (or more if you can!). You just need to practice thinking and talking at the same time.

The ability to concentrate is a skill like any other. Though you may be frustrated in your attempts to focus on a single task, you cannot expect your concentration to improve without patience and practice. Start by thinking back to a time and a place when you were able to concentrate. Then set attainable goals to ensure success.
Start by telling yourself you are going to complete one small task on your list. This will keep you keep you from being overwhelmed in the beginning. By the time you ease into work mode you might find you've knocked off several tasks, or even your entire list.
Reward yourself with a break between tasks. Use the time to get up and move around, call a friend, eat a snack or do anything that will get you energized for the next round.
Set attainable goals for yourself. When scheduling work time, take into account how you are feeling and how interested you are in the task at hand.
Attempting to work when you are tired and/or hungry is frustrating and not very productive.
Good luck:)