I have seven warts on my right hand, What causes them, and how can you get rid of them? I tried the freeze away,and wart remover from the drug store, and went to the dermatoligist 3 times to get them removed but it didn’t work. Whats causing them,and how can you get rid of them?

I got a wart on my index finger about two years ago and have tried every over the counter remedy to remove it. The problem is- now I have several smaller warts that have appeared and I cannot get rid of them! Its frustrating and they are sooo unsightly! Got any suggestions on how I can safely and effectively remove them?