I am 33 years and my penis when erected it is 4.3 inch and one thing I got noticed is that when erected my penis or when it is not erected the portion of penis is conchy shaped.my niece involved in sex and she masturbated my penis and discharged some white substance.I tried to insert my penis into her but the attempt made her to get pain as my penis is more circular just seems to a (conchy shaped --like the tip of penis is thinner and middle portion is more circular).please give necessary medical suggestion so as to have safe sex with her.