Dear Welcome to HCM We understand your concerns I went through your description. I suggest you not to worry much. Visible vains on the penis shaft is quite normal. In fact they indicate good bloodflow and good strength to penis cells. Masturbation habit is not a sin. Everyone masturbates. Even animals do it. Masturbation once a day is normal upto the age of 18 or 19. When our priority changes, the habit reduces automatically. But anxiety asssociated with masturbation is dangerous. You need to be aware of masturbation and do not get anxious about it. You are unable to sustain erection because you are anxious about yout masturbation habit. You might need sexological counseling. I can help you through telephone. Contact me through customer care at www.healthcaremagic.com Hope this answers your query. Available for further clarifications. Good luck.