I am not a virgin...If I go to a gynecologist to diganose my problem. Will it b known to her dat I am not virgin?

Of course! But. .. The doctor will know a patient is not a virgin the minute the patient tells the doctor! Of course, if the patient doesn't tell the doctor, the doctor won't know, and will have to ask the patient, or will have to guess. On the other hand, the virginity thing is highly over-rated, and not very important except in issues of pregnancy, std's, psychological symptoms, and unfortunately, sexual assaults.
Yes & no. Lack of an intact hymen is not a particularly telling finding. It may have never formed, been traumatized riding a bicycle, or disappeared as you explored your own sexuality alone. If you acquired a genital, vaginal or cervical infection that is normally passed during sex it will be a bit more obvious. The ave age of 1st intercourse in the us is <14 so it is not a surprise to most drs. Talk it out.