When I Have Sex Within First Seconds I Ejaculate And

when i have sex within first seconds i ejaculate and my penis drops before my partner reaches orgasm.it will take me long time to erect again for another round.some times the second round i don't release making my partner get disappointed.as i speak now we parted ways with my wife,who left me for another man claiming that i don't satisfy her.what might be the problem with me doctor,and what can i do to correct this situation.plz hlep.