Hi i understand your concern. Male erection is hormonal function and based on sex drive. Erection occur due to increase blood flow in penile vein due to hormonal effect and sex drive. Yes sperm is the key to get baby Less sperm count may lead to pregnancy but it depends on several factors like No of sperm, Motility of sperm, Viscosity of female cervix, Function of female reproductive organs etc. You need proper knowledge about all this. Please read in net about all for more education. If still have a query then feel free to ask. Happy to help you. Thank you.