Premature ejaculation can indeed be a possible diagnosis in your case .
The most useful exercise for premature ejaculation is start-stop technique.In doing this exercise you have to obtain an erection through self-stimulation, or masturbation . After achieving an erection, stop stimulating yourself until you begin to lose erection; at that point, begins to stimulate again. Gradually, over a period of several weeks, you will gain ejaculatory control.
Other useful exercises for you are Kegel exercise.( Kegel exercises )
Also avoid smoking,tea,coffee.Take fresh fruits and fruit juice also herbs like asparagus are also used with good results .