You say that erection occurs within seconds followed by fast ejaculation.
Premature Ejaculation (PE) is very common and is usually not associated with any disease.
However it is sometimes associated with infection of male accessory glands, which is treatable.
You can learn to control PE by doing the kegel exercise - pull your muscles that you pull at the end of urination for few seconds then release, repeat this several times daily.
Another method to overcome PE is the stop-start technique - when you feel that you are going to ejaculate, stop the sexual stimulation and divert your mind, the penis will relax, after sometime start the stimulation again and repeat the procedure.
Over a few months you ejaculation time will gradually increase.
There are medicines which can delay ejaculation. We can start medicines if necessary.