Hello. My age is 25 years. The size of my penis is 9 to 10 cm when erect, but at rest only the head of penis remains out and I feel very embarrassing due to this. I don't have any other issue with it but want to know the reason for small size when it is at rest and also want to know that why there is a huge difference of size at rest and when it is erect. I have heard that it is due to lack of supply of blood to the penis and due to poor development of genitals. Please advise me if I need to consult a doctor and also advise can the size be increased without under going any operation or not.